If you’re truly long-term looking at FL. AA/MIA if you live south of TPA/St. Pete or DL/ATL if you live in or north of those cities.

MCO for UA will likely close in the next major downturn before its adds another category/expands it’s never gonna be one airlines hub (e.g. nowhere to expand, too low fare, too much competition). The U.S. southeast is a clear weakness in UA’s network and right now no potential to grow; just like Delta in TX or AA in pacific NW. Plus, the second you get tired of driving to fly a 737 you’ll be commuting to EWR/IAD (low frequency/lots of commuters) or IAH (senior base, low frequency, lots of commuters) both of which are mostly on 737’s (1 JS can’t be reserved).

FL commuting to ATL does have high loads, but bookable JS, high frequency on large planes, yellow slipping to only need 1 commute flight, and P.S. on the backup makes it much easier than people make it out to be + it’s an hour flight or less. ATL is also HQ (career opportunity/training center) and has 5,000+ pilots based there, seniority will always move steady there, and WB flying is night&day better than MIA. Pure speculation, but Delta is doing some interesting growth in Tampa; being the anchor tenant for new terminal/gates. Maybe a MCO/TPA 320 or 737 base once fleets consolidate more? Delta already does intl. & domestic WB flying out of TPA and MCO on their own metal with Skyteam in general dominating the TPA/MCO market.

If you can drive to MIA in south Florida that’s a clear winner. But, AA/DL’s financial performance would be a factor in on my decision as well and how you see each company performing in the near & far future.

p.s. these are my own opinions/experiences on the matter. Please take it as such