My only preference is to play with my bro. We've been playing together for almost 10 years (either on one computer switching back and forth, or for the last 4-5 years, seperate, but on one team) and we've developed such a great teamwork style that we can always depend on eachother, it's kinda nice to be able to do that. And since he's sniper and I'm more automatic weapons, we make for deadly shit... We do (one of us, at least) get swapped and we deal with it. But one thing's for sure, we love losing sides man.
I think Bman does help out, I've witnessed it many times. Either way, if he does end up on the winning team, it's circumstance, not because he 'chose' to stack. He's definately not in the class of the aforementiond people who 'intentionally stack'.
/2cents
EDIT: Spacing... always fucks me.