Treyarch because of zombies and maps with flanking routes.

Yeah, they put new things in the game not like infinityward which just add a character and call it a brand new game.

Story: Treyarch takes the cake here by a long shot.

MP: Hard to say.. both sides just went downhill after Cod4/MWR and WaW. It's now a case of which is the lesser of two evils and even that is situational.

Co-op: I personally have to give it to Treyarch here. Survival mode can be fun but simply does not beat blowen heads off of zombies.. even if the zombies are lagged as all hell.

DLC: I cannot speak from expericance as the only DLC i have ever dowonloaded was for MW2. From what i hear Treyarch makes better DLC maps but it's all just personal opinion.

Feel: When it comes to the controls you simply cannot beat Infinityward. Their games haev always felt right as oppesed to their choppy and lose colleagues.

Map design: Again this is HIGHLY opinionated. I prefert the strait-forward maps with tight lines of sight and sharp corners. I cannot stand the large open maps Treyarch seems to like so much.

Balance: Each game is has it's on balancing issues. To say MW3 is more out of balance then BO (same goes for MWR and WaW as well) or vise versa is BS. They are two differnet games with the same name.