I think the different data centers have less difference than people think.

Yes it is true that RPers congregated on Balmung because you need to have others of like mind around you to do RP. But it has also long been a hotspot just because it was big - and so attracted a lot of other types of players as well.

Now that I am on Crystal I have some some extremely hardcore raiding types show up in Party Finder hailing from Crystal. I have also met extreme casuals back when I was on Aether.

I think it really just boils down to whatever server you happen to first find a group of people you can along with on.