BF3 AND MW3 are apples and oranges. Completely different playstyles.

If you want cooperative play go with BF3.

MW3 and COD in general, is nothing but run and gun.

That said, I played the BF3 Beta and was not very impressed. Takes too long to get into the game. I didn't like having to run for miles to get to the objective (I know you get vehicles in the actual game). Didn't like being sniped from across the map either. I'll stick to run and gun.