Exactly this! There are great people to work with and terrible people to work with at ALL the airlines. Really you need to make the decision based on where you want to live. Commuting to work sucks! If you have your life established in an American/United base there is great value in waiting to see if you can can get a job with one of them and not uproot your established life. 6 months is a long time and a decent amount of seniority above you when you eventually flow. But the hard cost of commuting to work, staying in a crashpad, offset by getting to keep your bonus money is something you need to ultimately weigh against your bird in hand offer from Delta. Good luck with the decision!