I don't prefer either of them, because all games are good they're own way.
Of course, I play/Like Call of Duty. I really don't care how it looks, how much we talk about "Teamwork". If you talk about Single Player, then there is a Teamwork, and in MP, there is also Teamwork, you just don't see it.
All games are different, there is no single realism in these both games. If there would be realism, then pretty much all FPS games should have a 'Bullet drop' and also a Wind and such. But where are those 2 things in CoD/BF ? No where.
Only game I know where is 'Bullet Drop' is a game called 'Sniper Elite v2'.
I prefer CoD:Ghost. I don't care if people prefer CoD or BF. They both are good.
No need for CoD / BF War in here -.-