Tera on steam is the north American version. having played both European and NA versions I can say the NA version is much much better. The game is the same but the people who run it are different. En Masse who do the NA version do a much better job of it and I get less lag on the NA servers than I do on the EU servers plus there is a really healthy EU community on the NA servers.
I play TERA, WoW, SWTOR and FF14. From time to time I play a bit of GW2, ESO and Wildstar.