I'm not sure why exactly these games are being compared, they are not so much siblings as they are distant cousins.
OT: I'm getting tired of Nuke boosting in my FFA (my main mode in MW2) and how Activision isn't really doing much to fix the other problems. I like the game I really, really like the game but I'm at the end of my rope here, the few really good things about it are being overwhelmed by the mountain of problems. Exacerbating the situation is the fact that my main gaming pals have abandoned it.
Battlefield on the other hand I've had a better experience with. I LOVED the single-player of Bad Company one, even liking it better than COD4 (I know that's heresy to some but that's how I really feel) but I never really got into the multiplayer for one reason or another. I thoroughly enjoyed 1943 but discontinued playing due to repetition and the fact that every time I try to join a game recently, I can't find one. I really liked the BC2 Demo and the single player looks better than the first, so I have high hopes.
That being said, I also think other games are looking promising as well, I'm all but guaranteed to sign up for the new Ghost Recon game's Beta (HOLY SHIT! HOLY SHIT! Did you see that trailer?!?) plus Conviction's multiplayer is looking awesome as well, so we'll see.
By the by I noticed your poll is severely lacking... well a poll. Are we going to remedy that somehow.