At the end of the day, I think it really comes down to where you are based and what routes you fly. Always making a connection just to consolidate FF points, I suspect would get quite old.
I'm currently based in HK, but not sure for how long, so do not personally see the value in MPC, but Oneworld carriers have met 90% of my travel needs this year. The US based programs tend to be the most generous (tier bonus'), and Cathay treats OneWorld elites exceptionally well, so for me AAdvantage is the clear choice as I get the best of both worlds.
The only downside is as christep mentions:
Originally Posted by christep
they would have counted towards AA status (assuming they were of a mileage earning subclass).
You do have to be vigiliant about fare class's if you are flying in economy, as generally each partner airline has it's own rules. So that said, while I am not in the MPC, I do have an asiamiles number. If I want to book a cheap Cathay flight, I put my AA number in the booking so that I can have lounge access and a shot at an op up (surprisingly common for elites on Cathay), and about 30 minutes prior to departure switch it to my Asiamiles number. Again for me, the best of all worlds.
The funny thing is that my initial qualification for AA gold was on CX, AA plat on CX, and next week EXP qualification will be on a CX flight as well.