I play MW2 on PC often and BO when I visit my nephew on PS3. I'm not very great though. I'm much better playing with a mouse on the PC than the PS3 controller. I just can't get used to the controller.
After playing BO, I prefer the currency format than in MW2 that you had to get so many kills then complete the challenges to unlock attachments (ie. The AK-47 is level 70, requires 300 kills to get FMJ and then another 40 bullet penetration kills to get extended mags). With BO you just get the currency and unlock the attachment you want.
The part where BO sucks is the gameplay itself. Too many connection interruptions, host migrations. The matchups can be so unbalanced it's a joke. Also, it could be my skill level or using the PS3 controller, but there's been far too many times where I've had someone dead in my sights with a strong gun like FAL or M16, fire off 3, only hit 1 or none, and then get killed by his 1 shot. :scratchhe Also the snipers suck in BO, which is good & bad since MW2 QS cheaters are annoying. On PS3 I haven't noticed any cheating, unlike playing on MW2 PC there's a lot of cheaters using aimbots or no-recoil cheats, so that is not fun.