I see a lot of people talking about the differences between the two biggest servers, I thought that I might try to iron out some misconceptions. Some of the big things for the two servers:

Ephinea
* PSO2 style drop system (individual drops)
* Lucky Day system (class/character based rare item drop boost)
* Hunters boost road (quest based item drop rate boost)
* Hardcore mode (one life mode)
* Sandbox mode (use commands to test out characters/items)
* English/Japanese Language support
* Milestone events (serverwide bonuses based on monster kills)
* Leaderboards and TA events
* Custom Commands
* Lobby Jukebox
* Can use modded skins for items and areas
* Shared bank by using the /bank command * Team Functions need to be unlocked

Ultima
* 3x xp boost to 165, 2x xp to 200 (can be turned off at ANYTIME)
* Custom items (added by GMs)
* Increased Rare monster rates (with adjusted starter rare drop rates)
* Buffed Ultimate mode
* Increased Max stat cap
* Donation system with rewards
* Multi Language support (Spanish, Portuguese, French, Japanese, English)
* Ability to use modded skins and /NPC command for character models (for items, areas, etc.)
* Shared Bank by using the /bank command
* All team functions are unlocked
* Custom Commands
* Mini Events that allow you to add HIT/Create or fix MAGs/Adding special to weapons

You can see there are some big differences between the servers, and they each offer some interesting things. You can keep the XP rate at x1 for both servers whenever you want, you can find ways to increase your drop rates on both servers, while the PSO2 style drop system is something that is currently unique to Ephinea, Ultima is in the process of implementing something similar (it's complete and in the testing phase right now). Ephinea has declared that they won't be releasing custom items, Ultima has a fair amount implemented in game. You can donate for items on Ultima as a way to support the server, Ephinea does not have a system for this. It's hard to call either server vanilla, given the amount of additional features added (regardless of whether they are opt in or mandatory). What your choice will finally come down to is the community; both of the games have strong communities, nice and friendly players and fun community events. If you have friends on a server I would say play there. If you are pressed for time and just want to dive in and relieve some glory days play on Ultima, as it will have the added benefit of giving a bit of longevity (not necessarily over Ephinea, just in general) in the form of an over tuned Ult mode should you find yourself wanting to stay longer. If you are interested in something with more unique features and some QoL improvements to the base game choose Ephinea. It will be slower, so make sure you have more time to invest. Both servers are great though, don't let anyone tell you one is more "vanilla" than the other, as that is absolutely false.

I hate reddit formatting, apologies if it is hard to read.