EC: Oligarch, Vix, Perdan, Xavax. They seem the most interesting/lively realms at the moment. Personal preference though. It might be equally interesting to join a smaller realm (Alara? Minas Nova? Shadowdale? Eponllyn?) and see it kick to life.
BT: Thalmarkin, Nothoi, Fronen. They look the most promising realms in the onslaught, though I agree with the notion of Delvin that Thal might ultimately be the last realm standing up to the invasion.
Dwi: I'm in LN. It caved in on itself after it caved in the world. The cards are so reshuffled on Dwi, I don't really know anymore. Plenty of options.