Im in the opposite shoes, well, I was in those shoes up until today, and made the final decidion a few hours ago when I booked my first trips away from DL.

Im a long time NW Plat, now DL Platinum, was looking to switch to either UA or AA. After a long decision process, I chose UA. However, in your case I would just stick with AA.

The main reasons I chose UA over AA is UA's Asian network and the fact they fly to DME. Other then that, I would have chosen AA.

Completely agree with other posters that AA program is superior to anything else in the States now, but in some instances like my own, where very specific personal travel patterns play in, AA looses a little bit. In your case, however, stay with AA! Happy travels