I LOVE splitscreen online zombies. I'd give that an A+.
In multiplayer, it's okay. I don't really have much use for it, as I only have 1 usable controller, the other 2 are from 2006 & have messed up analog sticks. When I have friends over, I really don't want to sit around and play Black Ops. If we played video games, it'd be something like Madden.
To the point of the OP, I've found that the (2) person always does worse, and always camps harder. I usually don't get on teams of the splitscreeners though, I try to stay in large parties with friends.
In S&

, usually half of the team will go -KDR; no matter it be on splitscreen, or singleplayer.