I enjoy getting upgraded to F so I would go with AS, even if it meant taking less convenient flights. You obviously aren't guaranteed to get upgraded as MVP, but with AA you don't get upgrade certs until you fly 35,000 miles and you would have to use all four on a one-way flight DFW-SEA.

BUT since you want to rack up those RDM, only switch to AS if you can status match and get your 50% bonus on all AA, DL, and AS flights. AA only offers 25% bonus at the Gold level.