That really depends on what you're looking for in an FPS game. Call of Duty is more along the lines of killing everything that moves and not bothering to ask questions later, where as Battlefield seems to be more about working as a team to complete your collective goal.
MW3 is new but old. Same as the rest of the games Activision pumps out every year. You can play it with your eyes shut and still do better than half your team. BF3 requires more team work, there is not so much room for being a lone wolf hero if you want to win. Also requires a little more cognitive thinking during the game than MW3. All FPS games have campers, so that's not even worth bringing into the discussion.
In battlefield games you can easily make top score as a medic without even firing your gun or do objectives.You actually have to think less in bf on objective based modes cause there is always a medic to revive you.1 good medic is all a team needs to win.
I say Bf3, because MW3 is a overrated game that just has some weapon changes and a different campaign, but it really is just the same game as MW2. Bf3 on the other hand has great graphics, intense combat with lots of vehicles and weapons, Jets also, and has some awesome maps with a lot of great players. Also, like Nurse said, you actually have to use your brain and work as a team, I have been in many situations were me and the squad I joined in a random game were moving together, covering each other, and being like an actual military unit in a way. But hey, that is just the opinion of someone who has been gaming there whole lives!
I wasn't being mean. I said it doesn't appeal to me at all, because I've played those games and simply didn't like them. Sorry if this offends you, I just simply would vote no to both of these games if they were up against Skyrim. Otherwise, I'd take MW3.
MW3... I used to think it was a gay game.... then i started to like it again... idk why? ha ha ha but i think that its a cool game
BF3 by far, its realistic, has teamwork and mature players, and not everyone is a tryhard. plus the world is responsive and you have vehicles, The between rounds lobby lacks a little something but overall the GUI, and all aspects of Bf3 are better than No recoil no damage, all tryhard, COD series, Dont get me wrong i still like COD But BF3 is superior in everyway