As usual, Global ratings are my own opinions relative to other character or TMs available at the time this is written (effectively, rating on a curve where a 10/10 unit is the best, or tied with the best, at this exact moment -- not forever), with Japanese ratings coming from altema.jp and are based on the characters current max rarity in Japan. Japanese TM ratings are on a scale from: Unranked, A, S, SS, to SSS.

QUICK DISCLAIMER: Both Sazh and Vanille have Global Exclusive Abilities that are yet (as far as I'm aware anyway!) unknown. I will update this post the day following maintenance to include those abilities (assuming they are worth mentioning -- if they aren't I'll at least update this disclaimer)

SAZH:

Rarity: 3★ to 5★

Global Party Rating: 5/10

Sazh is a negative example of Japanese stereotyping of black people "support" character with lackluster ATK (106 ATK 0%), an awful selection of weapons (dagger, bow, thrown, gun) and a solid set of equipment options (hat, clothing, light armor.)

For support he brings Full Break (160% Single Target Physical Attack and 3 Turn -30% All Stats).... and absolutely nothing else. Not even the ability to equip green magic. Only the moral support provided by his Frocobo.

Passively he brings... 20% HP... woo!

For white magic, he brings Curaga -- not to be confused with it's useful brother CuraJA, CuraGA is the least popular of the Cure line of spells. He also can't equip white magic to put any other white magic spells on him.

Offensively he brings a Multiburst (Critical Hit 100% AoE 1 Hit Physical Attack) and Sparkstrike (150% ST 1 Hit Thunder Physical Attack) but beyond that it's a collection of really lackluster attacks including TWO different 120% Single Target Physical Damage abilities (an illusion of choice!), a Critical Hit 100% Single Target ability, and a 110% AOE Physical Attack.

His Limit Burst is a 250% to 345% (depending on rank) AOE 13 Hit Physical Attack which, while isn't enough to make him a decent support or physical DPS, it is likely the second least disappointing part of his kit (after Full Break.)

Japanese Character Rating (altema.jp): 55/100

Global Trust Mastery Rating: Twenty-sided Die - 5/10 (READ BELOW)

Materia - 20% Chance to Dodge Physical Attacks 20% Crit

Analysing this materia is complicated and I fully expect (as I've done a few of these now...) that my rating of this materia will be the sticking point on this review. Critical hits are a flat 150% modifier on all attacks. 20% Crit can then effectively be seen (but remember, RNG can be a real bitch sometimes) a 10% damage increase on top of all other modifiers. Let's do some math to compare this to 10% ATK and 20% ATK materia, shall we? (I'm not including 30% because you have, at max, 1). Let's assume a 6★ physical attacker and let's give them 150 ATK (I know not everyone has a 6★, and some are higher or lower, but I worked all day and you don't pay me so let's just consider this 'good enough' okay?.) I'll use the arbitrary DEF value of 100 (because it doesn't really matter when comparing thresholds -- the DMG numbers will change but the break-points of which materia is better will not) and I'll use Barrage as the ability (because it also doesn't matter when comparing ATK values, you guys hate Barrage now, and it was a long day.) All attack ratings are AFTER GEAR (not base):

edit: Barrage can't crit. I knew this and should have picked basicallyi anything else -- of course that's the random ability I chose. Meanwhile the breakpoints above still apply to abilities that CAN crit

As you can see above, this materia barely beats your free 10% ATK materia at 300 ATK, but doesn't start to overcome a 20% ATK materia until 700 ATK.

TL;DR: Shamu will find a marginal increase with this materia over a 10% or 20% ATK materia -- for PVE the rest of you can ignore it.

As for PVP? Some people seem to swear by the 20% chance to dodge physical attacks but at this point Exdeath is my biggest worry in Arena but feel free to disagree below! (As mentioned by /u/Rozaliin below, this is often stacked in Japan for Arena -- read their comment below)

Japanese TM Rating (altema.jp): Unranked

Why would you want Sazh?: It seems like just yesterday I said "when the worst unit on a banner has Full Break, you know it's a great banner" but that was nearly a month ago and times have changed. At this point, we've had Full-Break user after Full-Break user and Sazh is absolutely the worst. So I guess, if you do want him, it's because you still don't have full-break or you particulary like his character but I have difficulty believing there are many Sazh fans out there. As mentioned above there are niche situations where his TM is a minor DMG gain over alternatives.

Is he FUTURE-PROOF?: No. Sazh does not currently have a 6★ upgrade in Japan and has not received Ability Enhancements.

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VANILLE:

Rarity: 4★ to 5★

Global Party Rating: 6/10

Vanille is a support? healer? filler character with decent SPR (118 0%), a lot of weapon options (rod, staff, harp, whip, mace) and solid equipment options (hat, clothes, robes.)

For support skills, Vanille brings Cheer (AoE 3 Turn 40% ATK/DEF) and Focus (AoE 3 Turn 40% MAG/SPR) which are great if you don't already have better characters to bring them. She also brings Deprotect (3 Turn -20% DEF) and Deshell (3 Turn -20% SPR) but at this point let's just assume you bring Full Break (or better) or don't feel you need these debuffs.

For passives, Vanille brings 20% MP.

Offensively, Vanille brings absolutely nothing but, perhaps, her signature suggestive moans.

For white magic she brings: Cure, Cura, Curaga, and Esuna but not the only heal anyone cares about now -- Curaja.

Her limit burst is a 70% to 89% (depending on rank) chance to one-hit KO. (As suggested by /u/Rozaliin -- this, at max rank, is commonly used in Arena in Japan. See their comment below for more details. CTRL F is your friend.)

Japanese Character Rating (altema.jp): 75/100

Global Trust Mastery Rating: Magistral Crest - 8/10

Accessory - 30% MAG/SPR

Better than Earrings, this is the best Mage accessory currently on global. If you're only using Mages in PVP, you're likely damage capped without these -- if you're using Mages in PVE you probably wish you weren't on anything that lasts more than three to four turns. If you DO value mages in PVE these are best-in-slot until Exceed Ring (which might as well not exist, unless you're insane.)

Japanese TM Rating (altema.jp): S Tier

Why would you want Vanille?: If, for some reason, your A-Team lacks both Cheer AND Focus she has both. Otherwise her best attribute is her TM.

Is she FUTURE-PROOF?: No. Vanille has not received 6★ in Japan. She has received Ability Enhancements which increase both Cheer and Focus from 40% to 55% and lowers the mana cost from 48 to 36 (thanks to /u/scathias)

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SNOW:

Rarity: 4★ to 6★

Global Party Rating: 8/10

Snow is a damage tank with decent ATK (138 ATK 0% unless unarmed -- then 50%), with an awful selection of weapons (dagger, thrown, mace, fist) and a not-very-tanky selection of equipment (light shield, hat, clothes.)

As a tank he brings 'Draw Attacks' (Increase likeliness of being targeted by 50%) but he pairs that with Counter (30% Chance to Counter Physical Attacks) and Fighting Spirit (30% Chance to Counter Magical Attacks) -- both of which combine with Eye for an Eye (Double chance of countering) contributing to more overall DMG than Cecil, WoL, Charlotte, etc.

For support, Snow brings Battle Roar (AOE 3 Turn 50% ATK and inflicts 2000 DMG to Snow) but is likely not worth the 2k HP hit over Cheer or Embolden.

Passively, Snow brings the aforementioned traits I listed under tanking as well as HP 30%, DEF 20%, and HP Stroll (Recover 5 HP while walking every 3 steps -- which is as unexciting as it sounds.)

Offensively, Snow brings Aquastrike (150% Single Target Water Physical DMG), Froststrike (140% Single Target Ice Physical DMG), and Area Blast (180% AOE Physical DMG.) He also brings some offensive magic that you'll never cast.

His Limit Burst is 290% to 410% (depending on rank) ignore 50% DEF physical damage to one enemy (normalized to 580% to 820%) which can be very impressive with enough ATK.

Japanese Character Rating (altema.jp): 89/100

Global Trust Mastery Rating: Champion's Belt - 8/10

Accessory - 30 ATK / 30 DEF. 20% ATK/DEF when equipped with fists.

This is a very solid accessory -- even without a fist equipped 30 ATK is pretty much the bar for a physical accesssory at this point. The only problem is there aren't a lot of great fists. The best fist we have access to the Kaiser Knuckles (101 ATK - Wind) but the wind element can be cumbersome. This is not as good as Gaffgarion's TM (or Luneth's TM) if you're not using a fist, but best-in-slot if you are using (or can use) Kaiser Knuckles or if another fist is one of your better weapons.

Japanese TM Rating (altema.jp): S Tier

Why would you want Snow?: No Cecil? Snow is the best alternative for a 6★ tank today. His TM is good to great depending on your gear options.

Is he FUTURE-PROOF?: Yes. Snow comes with 6★ but he's greatly outclassed by 6★ Cecil (or somewhat soon, 6★ WoL.) He has received Ability Enhancements including a 40% Chance to Counter Physical Attacks, 40% Chance to Counter Magical Attacks, and only taking 500 damage (instead of 2k) to AOE boost ATK by 50% for 5 turns (instead of 3.)

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SHOULD YOU PULL?: No. Unless there's some TMs you really want, or you somehow missed out on Cecil but somehow think you'll have better luck with a 4★ base (and inferior) tank this banner is super skippable. These characters weren't good when they were released in Japan and we are getting them SUPER late.

(BY POPULAR REQUEST) SHOULD YOU PULL JUST FOR EVENT CURRENCY?: There's nothing absolutely MUST HAVE from this event outside of the usual suspects. Expect that next week we'll have a banner of Fang, Hope, and Lightning (SPOILER: Fang and Hope also aren't exciting -- Lightning still is) and expect them to have a 50%, 75% and 100% currency modifier respectively (DISCLAIMER: I don't know any of this for sure as I'm not clairvoyant, but I would be surprised) and you can likely get the important rewards just by bringing whatever friend unit this week and a friend Lightning next week.