Depends, you know? Sometimes the reason for co-op is a vast difference in ability, and you don't want to baby-sit your team mates. I like playing COD Black Ops co-op vs bots with my friends because I'm really good, and they are not. If we play vs. in any FPS, it consists largely of me killing them without them having any idea of what they're doing. Put us all on the same team vs. bots, though, and it gets really fun.
For example, a couple weeks ago we were doing 3 vs 9 on Array. I was just tooling around the map, being my regular COD-playing self. Sometimes, I would camp for a while and snipe so that they could have more fun killing bots. At one point, they both teamed up, threw out a care package (which is total bot-bait) and just farmed kills. They had fun. I had fun. They didn't interfere with me, and I didn't interfere with them.
For example, a couple weeks ago we were doing 3 vs 9 on Array. I was just tooling around the map, being my regular COD-playing self. Sometimes, I would camp for a while and snipe so that they could have more fun killing bots. At one point, they both teamed up, threw out a care package (which is total bot-bait) and just farmed kills. They had fun. I had fun. They didn't interfere with me, and I didn't interfere with them.