I’d argue that making a decision for a long career based off of current contracts between two legacy airlines is a fool’s errand. Delta just got their contract, and we’re negotiating our next one. Looking back 20-30 years I’d bet that the difference between the two isn’t that great. Going forward I’d expect that trend to continue. Either would be a good choice, pick the one with the easiest commute or a base that you’d be willing to live in and enjoy the ride.