Best Zombie Apocalypse MMO?

UdoD

There seem to be a lot of zombie apocalypse games coming out simultaneously.  Can anyone either widely read or currently in some of the beta's clue me in to which of these titles seems most MMO-like, with a persistent world / basecamps you can build and defend, geared for the PC platform, and features nice pvp as well?  I am not interested in just playing a shooter zombie sim.