I played on all server.
Here my resume:
4Nova:
Pro: Nice Events
Pro: Devs trying their best (good patches)
Pro: on TW is nice PvP
Contra: Player base isnt that big for my opinion if you compare with Papaya 4Story or 4ancient
Contra: The admin Team is corrupt (see statement of godlike on epvp) or for example: Ramon is the admin of 4Nova but has full +23/+24 eq on his Private Account and his friend Dali tried to sell Golds to me like wtf?)
4ancient:
Pro: Big Community (good population)
Pro: Good Support (fast Communication)
Pro: Nice patches (to be honest i like Nova patches more)
Contra: You need some time to get fast good Equipment but its possible!
Contra: not enough PVE content like dungeons or smthing like that.)
Papayaplay:
Pro: good population between 18:00 and 23:00
Pro: every week patch
Pro: its an official server
Pro: nice PvP on TW / BoK/ Skygarden
Pro: easy to get fast good Equipment (cause server is new and standart is 16-18
Contra: Support needs a lot of time for answering Tickets.
Contra: Communication between Team is not good (they need more GM's)
Contra: not enough content like on Ancient or Nova
Contra: Server is on NA
All in one every server has pros and contras.
You could try every server but for me atm is only
4Ancient and Papayaplay the way