I just finished the game up to the end of E18 on the Redux version and really enjoyed the game. I roped some of my friends into trying the game as well but they're playing the base game, which I've never actually played, so I wanted to get some opinions on how Redux's fights compare to the base game, in terms of challenge and design, to see which one I'll play for my subsequent playthrough. I'll include my thoughts on the Redux Master fights as those are the ones I fought and I don't know how many people have actually played Redux on this sub. All of these fights are Master Mode, which forces the "Set" battle style regardless of your in-game selection. They're either singles or doubles, which I'll denote for each gym.

As a side note, I thought most of the battles in Redux were very well designed (I did the master fight for all of the gyms fiore gauntlet and glass gauntlet, so I'll describe those).

Julia (Doubles): Luxio, Togedemaru, Emolga, Stunfisk, Electrode, Charjabug
Togedemaru is really bulky and I chose torchic as my starter so having to rely on physical moves for this gym was awful. In the end what carried me was using Loudred spamming echoed voice, as Emolga, Stunfisk, and Electrode are all seriously difficult pokemon to deal with at this stage of the game, especially without a rock type to deal with Emolga spamming Acrobatics. The fight overall is pretty fair though, there's plenty of ways to set up on this gym especially with an espurr being given to us to use fake out and help our sweeper get rolling.

Florinia (Doubles): Alolan Exeggutor, Torterra, Steelix, Hippowdon, Cradily, Amoonguss
Florinia's Master fight is ridiculous. Frankly this was probably the hardest Gym up until Titania's, but there's a very good reason this gym was nerfed by Commander. A level 24 Torterra and Steelix aren't exactly normal threats to deal with at this point in the game. The nerfed fight includes much more reasonable pokemon like Gogoat, although the team is pretty specifically designed against physically-based pokemon, so my starter choice was definitely not very good here (my starter actually ended up benched after Aya for the rest of the game, as Blaziken just generally isn't that great of a pokemon to deal with a lot of the challenges in this game as bulk is such a massive boon over most forms of speed control). The fight itself was essentially just a balancing act of baiting attacks into immunities or resistances by constantly switching, while trying to keep my ice-type pokemon free of harm as they sweep the gym. This is true in the nerfed version as well, with the difference being that vanilite actually doesn't need that much support to sweep the gym in the nerfed Master version.

Corey (Singles): Tentacruel, Toxicroak, Skuntank, Scolipede, Zangoose, Crobat
Shelly (Doubles): Vivillon, Victreebel, Galvantula, Armaldo, Yanmega, Scizor
Shade (Doubles): Alolan Marowak, Rotom-Wash, Froslass, Decidueye, Gengar, Chandelure
These gym leaders were frankly all pushovers. Corey was abusable with the steel type options available up to now along with nidoking from Onyx Arcade, Shelly was defeated through telluric seed abuse from blaziken and scolipede, and Shade got completely ran over by Sharpedo (aqua gang) and excadrill dealt with rotom-w (mystery egg). Nothing too special with these fights, I wish they were harder, although Shelly's fight despite being easy was a very good place to show how hard items can be abused, as I got the idea for telluric seed abuse from seeing her lead pokemon use it.

Kiki (Singles): Primeape, Lucario, Gligar, Lycanroc, Sawk, Mega Medicham
The first Mega gym leader in the game. This was a very difficult fight, all of her pokemon needed some sort of answer. I found the best way to do this was to use a core of Mawile, Medicham (event before the battle), and Excadrill who had answers to most of the team, and then using the rest of the team to support the core as a sort of Hyper Offense jank team. I had to use Jellicent and Nidoking to stall against her mega medicham, both baiting super effective moves while will-o-wisp slowly ticked her down.

Solaris (Singles): Volcarona, Gyarados, Excadrill, Stoutland, Tyranitar, Garchomp
Not a gym leader, but extremely difficult. Unlike the hardcore mod, his Garchomp is level 75, while the rest of the team is a fairly normal level. This entire team was absurdly hard to deal with, but I was able to succeed by intimidate spamming on the Pokemon before Garchomp came out, then using Destiny Bond Sharpedo to deal with said ace. This fight was unfair, but it's supposed to be unfair for the plot, as you can lose this battle and continue.

Aya (Doubles): Nidoqueen, Metagross, Salazzle, Mega Venusaur, Dragalge, Alolan Muk
This is the gym that taught me to abuse the field as much as the leaders are abusing it, because holy hell this field is literally perfect for Aya's Pokemon. Nidoking carried in this gym, although I had to soft reset a few times to make sure the elemental seed didn't paralyze or freeze him. All of my other pokemon were there to bait hits away from Nidoking, as they're all stupidly powerful and he dies in one hit. For her final two Pokemon, I brought out Medicham to try and kill the Venusaur, but I pretty much had to rely on Nidoking for the entire rest of the gym as nothing else I had at this point was able to deal with her mons effectively, as excadrill is rendered useless by the field effect. I'm not sure how I feel about this fight, because it seems like the only real way to beat the gym is by spamming boosted earth powers, and there aren't too many options for that besides the shellos and nidoran we get for free.

Serra (Doubles): Froslass, Mega Glalie, Mamoswine, Cryogonal, Cloyster, Weavile
This gym was extremely difficult. It takes place on a Glitch field, which is extremely dangerous because all of her pokemon spam blizzard, and automatically starts with Hail. Not a single thing I was doing actually worked on this gym for the longest time. Then, I remembered that seeds exist, and looked up what a seed item would do in this field. It gives some defensive boosts and transforms the holder into the BIRD type, missingno's type with no weaknesses. I also noticed that I had a shedinja. The only thing that could stop shedinja in this gym was hail, which I dealt with by using Poliwrath to set up rain. Shedinja 1v6'd the entire gym.

Noel (Doubles): Gothitelle, Tauros, Staraptor, Mega Pidgeot, Slaking, Clefable
Radomus (Doubles): Mega Metagross, Mismagius, Sigilyph, Medicham, Grumpig, Mega Gardevoir
Not much special about these battles either. Something to note is that Radomus does introduce the first instance of Mega stacking that opposing trainers will start to do. One of their Pokemon will mega evolve normally, the others will come in already mega'd and be able to hold an item such as a life orb. However, we have a lot of options to deal with those pokemon by this point in the game. I built a sand team for Noel as I wanted to start trying to use decently built teams by this point, and just got access to Hippopotas. This team worked for the next few gyms as well, including Radomus, without much issue.

Luna (Singles): Greninja, Honchkrow, Weavile, Umbreon, Alolan Ninetales, Mega Houndoom
By now it's pretty apparent that the favored format for Master Mode is Doubles, so when a singles fight pops up you know it'll be difficult. Luna is the first difficulty spike of the game imo besides Florinia, who I think is a bit of an anomaly. Despite not having double megas or any real gimmicks, her team is a hyper offense machine that abuses the field aurora veil to make her dark types super unkillable, so it's really just combining bulky offense and hyper offense. This took me a few tries, but Arcanine was really helpful despite Luna only having 2 pokemon for intimidate to work on. Weavile is simply too hard of a threat to deal with without fast pokemon with the ability to use fighting moves at this point of the game, so I used Mawile and Arcanine to deal with it. Aside from that, this fight is very well put together as your final test before the plot gate at Agate Circus.

Samson (Doubles): Heracross, Hawlucha, Conkeldurr, Kommo-o, Braviary, Mega Mawile
Samson seems like a pretty polarizing fight. He's pretty easy but this is the first fight where speed basically trumps everything, as taking a single hit from any of his mons is likely to kill you due to the field, similar to Radomus, but you have a few less viable options available to you now because Mega Mawile is a very hard Pokemon to deal with in this gym.

Charlotte (Doubles): Kingdra, Darmanitan, Chandelure, Typhlosion, Ninetales, Mega Manectric
Charlotte's team looks easy on paper, except for the small fact that there is no reliable way to abuse rain at this stage of the game as both drizzle pokemon are locked behind story progression (king's rock and pelipper are not available right now, so the only way to set up rain is by using rain dance, which is too slow and allows kingdra to kill the team without repercussions). I decided to build a Trick room team for this fight, utilizing the earlier event Solosis. Mega Manectric messed with a lot of the other teams I was planning, as it does have perfect type coverage, so it needs to just die before it can get a hit off.

Terra (Singles): Nidoking, Excadrill, Garchomp, Donphan, Gliscor, Mega Camerupt
Another singles fight, which is just as hard as Luna's. This takes place on the Desert Field, and unlike Florinia, her pokemon all abuse the field for evasion and speed hax. The fight is an rngfest all the way through, but it makes up for it by being a fight that you know the solution to, you just have to bring Pokemon that can actually deal with it effectively. Her Pokemon are incredibly bulky and due to the field hax this fight is probably best dealt with using some form of stall. One of the most fun "hax" fights I've played, I thought the rngfest would make this a lot less enjoyable to attempt than it was.

Celestine Cascade Gauntlet
Blake: Walrein, Weavile, Feraligatr, Rotom-Frost, Mamoswine, Mega Glalie
Sirius: Chandelure, Hitmontop, Tyrantrum, Seviper, Honchkrow, Mega Manectric
Julia: Electrode, Heliolisk, Eelektross, Magnezone, Rotom-Fan, Mega Aggron
Solaris: Excadrill, Tyranitar, Stoutland, Garchomp, Scizor, Mega Gyarados
This chain of battles was really cool. After the first grunt fight, you're forced to battle as Julia or Florinia for 2 of the next 4 fights (though Florinia faces a grunt). I'm told that this changes if you lost to Solaris earlier in the game though. Florinia's team is pretty much her Master mode team with a few modifications like adding Ferrothorn and Hippowdon, but Julia's is really different. You can choose the opponents for each, but Julia vs. Sirius specifically was the hardest part of this gauntlet as dealing with his Mega Manectric was very difficult, and the only Pokemon with consistent super effective moves against more than 1 of his Pokemon was rotom-Fan, who is a terrible Pokemon. Very fun encounter but if I didn't 1-shot this encounter I would probably have taken a break for a few hours between attempts, as it is a very long gauntlet on Master Mode, and there's no healing since you have a healthy team from Julia and Florinia when their fights come up.

Ciel (Doubles): Xatu, Gliscor, Salamence, Mega Pidgeot, Mega Charizard Y, Mega Altaria
Yes, Ciel has 3 megas. As has been the theme for the circus trio, speed is pretty much king here. Altaria is pretty bulky but honestly she's probably the least threatening mon on the team. If Xatu gets both screens off, the fight becomes incredibly difficult, so I opted to try and kill it before it could get either screen off. The circus trio as a whole was really fun, and Ciel lived up to what I expected after the hell that was the Celestine Cascade Gauntlet.

Adrienn (Doubles): Dragonair, Togekiss, Florges, Alolan Ninetales, Mega Mawile, Mega Gardevoir
Togekiss's entire purpose in this battle is to swap the field to the Fairy Tale Field, which sucked because at this point I was using a Sun team as I'd finally gotten access to all the Pokemon I wanted to use with the reconstruction of Reborn City. Adrienn is the next difficulty spike in the game after Luna, and he kind of has to be as you've been given TONS of options as you return to Reborn City. The Dragonair is more of a threat than it seems like on paper as well.

Titania (Doubles): Bronzong, Milotic, Excadrill, Mega Gallade, Mega Scizor, Mega Lucario
Titania and Amaria are both really, really difficult fights. Titania effectively removes her fire type weakness on her Steel types due to the field, and she has triple megas. One of her megas and Excadrill also come with a seed, which guarantees them a free turn with automatic King's Shield. This fight took a while to plan out but it was very rewarding to beat, especially after the downer that was the events before this room. I took the Reshiram path, so I'm not sure if this fight changes on the Zekrom path.

Amaria (Doubles Hell Mode): Politoed, Qwilfish, Starmie, Ludicolo, Alolan Raichu, Azumarill, Tentacruel, Pelipper, Seismitoad, Kabutops, Kingdra, Crawdaunt, Gastrodon, Rotom-Wash, Lanturn, Vaporeon, Wishiwashi, Samurott, Seaking, Lapras, Clawitzer, Mega Swampert, Mega Sharpedo, Mega Slowbro, Mega Gyarados, Mega Blastoise
Yes, Amaria uses all of these Pokemon. She also has 5 megas and a couple Z moves. She has plenty of ways to counteract your options to change the field, and this fight is extremely long, so your best option is pretty much setting up with a bulky offensive pokemon that can 1v26 as best it can. My option was Ferrothorn holding a seed to increase its Spdef and apply aqua ring, and spamming Curse using her first 2 Pokemon as setup bait. The entire rest of the team was there just to stall for ferrothorn to do its thing. I had 2 more stall-setup-sweepers to use in the form of Lapras and Mega Venusaur, but they didn't put in nearly as much work as Ferrothorn. The worst part of this was Mega Blastoise and Clawitzer, which probably shouldn't be a surprise as they had the hardest hitting fighting type moves on this roster.

Glass Gauntlet
I can't find the teams for the Master Mode of this fight online, so I'll say that the main change is that Luna's fight is no longer a joke as she fights alongside Commander himself, who uses a Sun-based team in this fight, so all fights are 6v12 with no healing. Radomus and Serra's teams complement each other very well and make the end of this fight extremely challenging. This is probably the hardest fight in the game.

Hardy (Doubles): Gigalith, Stoutland, Lycanroc (Day), Alolan Dugtrio, Mega Tyranitar, Mega Aerodactyl
Hardy is a rather underwhelming end to the game, his team is honestly kind of a joke for how much we have available at this point. Stoutlant just spams Thunder Wave, which can be annoying, but we have plenty of ways to deal with it by now. Commander has stated that he's reworking the fight for E19 if he can, and that designing this fight was really difficult, so it should be better whenever that happens. Aside from this fight, everything up to this point was really challenging and great.

That's everything I think. If anyone could give me your thoughts on how this compares to the base game that would be awesome. Thanks in advance.