Depends, if you want more in terms of pure content then get Dual Strike.
If you want a more balanced game, with still plenty of content (just not quite as much) and competitive online multiplayer, get Days of Ruin.
Either way you'll get hundreds of hours of gameplay out of it.
A game I'm developing with some friends:
www.xnagg.com/zombieasteroids/publish.htm
It is largely a technical exercise but feedback is appreciated.







