My airline of choice is AA. I got lifetime platinum status with AA. Only use Delta when going to the south - Geogia - where th fares are dramatically different. I have about 100K in Delta - see them as back-up in case I can't get on an AA or BA flight. The AMEX starpoints gives 5K bonus for each 20K tranferred - not double but 1.25%. It also allows for use with any airline whereas the Skymiles card limits you to Delta. Did have one when there were great bonus - which is why I have 100K (and MCI deals). If they offer comparable fares and convenience. - I'd vote for AA.