Ghillis is spot-on. Both new, off-the-street hires, will be dealing with a major with merger growing pains and related issues. However, at AA, the average captain age (post-merger) is much older than hired Captain age at SWA (post-merger).
with that said, AA (if the captain age theory is correct) should have a quicker move up the seniority chain. Plus, additional attractions like multiple airplanes, international destinations, etc tip the scales in AA favor.
at this point (2013), there is really no (in my opinion) attractiveness of SWA over AA. You want to stay domestic ? I am sure you can work that out at AA. "Financial security" of the company ? SWA yes, (they are not Ch.11), but long term crystal ball is anybody's guess.
those who think "SWA is bulletproof" need to look at history and study Pan Am and TWA. So, today, going to the "bulletproof" company, may not be any guarantee. In addition, I think there is opportunity in confusion and chaos, and for that I would feel that AA has opportunity.
I would go AA if it were me.