Basicly what Grasshopper said. These 2 are totally different FPS games (Well not totally, but close). MW3 is quake style (with higher graphics and stuff) FPS, where best aim and fast reflexes win (some tactics too) BF3 is like war simulation, with vehicles, and where good tactics and teamplay win. No that much need for fast reflexes or epic aim (unless you'r recon). I like them both equally much in their own ways :3