East has the biggest activity. But 95% of all of Easts wealth is in 5% of the players. Most East players are embarrasingly poor.
West has a fair bit of players, but the economy is shit. Its made it so everyone is either really rich (like unhealthily rich) or at least well enough off for any char they want. Selling anything under a 45 skiller or 20/5, 20/11, 20/17 charms is almost impossible
Europe Ive always heard has the best PvPer's (Skill wise). Apparently their market is relatively dead for trading, but you cant get a better PvP realm.
All 3 of the realms have their benefits and disadvantages.
Asia is just the shits though, straight up.