I got the game for PS3 because it was cheap and I heard the graphics were more stable on it (Not sure if there's any truth to this) and while I love the online, it feels a bit vacant (And seeing the number of posts in the PS3 section of this forum confirms my suspicions). It's really hard to find any objective-based games and sometimes its hard to find regular deathmatch games too.
So I've been thinking about selling my copy and trading it in for the 360 version because with multiplatform FPS games it always seems like the Xbox has the most players, but if the online is just as dead as the PS3's, I might not even bother and will just stick with the version I have now.