to me no hesitation between MAG and BFBC2, MAG is technically inferior, on my beamer I tought ouch this is a pain to watch, especially after MW2.
The teamplay in BFBC2 is great, provided that you have a good friendlist of good BF players, because if you are alone in a lousy team, then the game is really frustrating.
The game is out in 3 weeks and you can play the demo until then, by the way the snowy map in the demo looks (to me) a lot less good than the sandy map in the beta so the final game will look a lot better i think.