Honestly, I would go to whichever one allows you to be home based (which is what I did). Commuting SUCKS...driving to work is amazing! Also, you gain a little seniority by living in base. You'll be readily available for premium trips, will hold a line quicker, or you can sit reserve from home. You'll be more likely to take upgrades earlier, knowing you can sit short call at home. I'd gladly give up some seniority and $$$ to not have to commute. No crash pads, no stressing over the jumpseat or making my commute. At the end of the trip, no matter what, I can get in my car and drive home.
I was a 2014 hire at both and ran my numbers based on # of pilots on list, the month after I was hired. Bottom line, I was ~50% at 10 years, top ~25% at 15ish years and top 10% at 20-21 years. First half seniority was slightly better at DAL, last half it was slightly better at AAL. Realize a few things; this accounted for zero growth from DOH, DAL has hired ~3,000 pilots since I was hired and these numbers were pre-AAL/USAir SLI.
Some other things to keep in mind. At DAL, I already hold WB FO and could hold NB Captain, in my home base...both at 90% seniority. I could also hold 73/320 Captain if I wanted to commute to NYC (ref my thoughts on commuting above). I'm fairly sure that, aside from the E190, I would be years away from Captain at AAL. I'm not sure about WB FO at AAL.