Completely different gameplay! you cant really choose...

Personlly I Think cod zombies WonderWeps

CoD Zombies is more fun, (peronally).

Those are completely different zombies you can not compare them. With cod you are camping and surviving rounds. With l4d you are on the move and are on the look out for different things. The zombies have more numbers but are a lot weaker. They are different games.

They r both neat.
COD ZOMBIES-I think that making a shrink gun and the force cannon (or whatever) is pretty dumb. Gameplay is magnificent but u dont move around much unless u do laps which is kinda boring and basically only can do good laps on ascension. Graphics r great but could be a little more creative. Bums me out how u die quick unless u have Juggernaut.its cool u can adys(aim down your sights.) Its also pretty neat for its creativity and how its set up. its not something u will see in any other games. The last thing i have to say is about where the maps take place. i like how theres many maps of the zombies and most zombies in every map r different kind of zombies. Like NVA zombies or Nazi zombies or just regular people in gear. (personal opinion about cod zombies.)

L4D2-I like how that u gotta move around a lot and dont die as fast. its also cool how u gotta use alot of team work. (not saying you dont use teamwork in COD zombies.) You always gotta stick together. Or a special infected with get u when u r not looking. Its also pretty cool how u get to be zombies. and being the special infected is wicked cool. but it really suxs how u can not aim down ur sights like in COD. The last i have to say is that they could have added a little more guns. Melee weapons r good but not against a tank, nor are good against special infected(if using online) Other wise though. this game is great! (personal opinion of Left4dead2)

I can't decide on either game.
i like 'em both

THESE ARE JUST MY OWN OPINIONS!!!!