DL PM based in DFW. Gave AA a try after growing up flying DL.

1. Upgrade structure is more advantageous domestically. No 500 mile certs to deal with.
2. Fleet is standardized, refurbs are frequent and cabins are newer.
3. Onboard service is FAR superior - AA FAs yell "WHO'S BAG IS THIS, IT NEEDS TO MOVE", DL FAs just make it fit
4. C+ puts MCE to SHAME. AA MCE: Movies $9, no free food, no free alcohol.
5. Regional fleet: CRJ-9 and E175s are MUCH nicer than ancient pencil plane E145s.
6. DL merger is completed, and the consolidation and standardization is just recently completed (took close to 7 years). AA is just starting down this track and it will be a while before they have a fluid product.
7. INTL product is standardized. AA still flies 763s without PTVs. Sure the 77W is a beautiful bird but good luck getting on it TATL consistently.
8. IRROPS are flawless (aside from the fact that they actually occurred) and I have never once (knock on wood) had a DL flight cancelled. One look at a DFW monitor during a rainstorm and you'll cringe at all the red text.
9. DL.com. So many people hate on it, but it is so much more user friendly and has much more info than AA.com. It blows my mind that other airlines dont publish amenities (PTV/SAT, meals, power) for every flight. Bag tracking, anyone?
10. Would enjoy BA and QF codeshares, but AF and VS are good alternatives for TATL, with mainline and KE for TPAC.

Will hit DM this year for the first time, and I'm already over 50% on upgrades as PM.

I'm not loyal to Delta, even though technically captive to a hub. Here's why.

1. Flew the family to Europe in 2014 and 2015. Although Icelandair and Condor Airlines offered fares at or below $1000 (and better times/connections), Delta never cracked $1750.

2. I need to fly a family member to DCA for Thanksgiving, was able to book this round trip for less than 13,000 Southwest points & $5, never remotely a possibility on Delta.

3. Next business trip is to ABQ, Delta has dropped the nonstops (NWA always had at least 2/day, some summers 3/day) and offers connections via ATL or SLC for $550. Southwest offers connections thru MCI or DEN for $350 that take 1-2 hours less time.