First off, let me state I don't have experience on UA, just CO. I was a CO Plat last year matched from AA EXP and only flew domestic routes. I did not find CO crew to be any better than AA crew. I also was disappointed in the upgrade % as a CO Plat compared to an AA EXP. As someone who is primarily a leisure traveler on my own dime I never bought the fares on CO to get an instant upgrade or to really have any decent chance at an upgrade. On AA though, I've yet to miss and upgrade even on EXP heavy flights such as JFK-LAX/SFO (although I admit to one time out of 6+ using a SWU because I didn't want to risk not getting upgraded). I think different programs work for different priorities. After trying out CO as a Plat I decided that AA EXP is a better choice for me and my travel 'profile'.