I'm UAL and it's been great to me, but I'd say stay at LUV. Life on a WB is great, but driving to work beats commuting and the reality is, depending on his age, he's likely to spend much of his career at UAL on a NB, anyway. He's already in class at SWA, so he'd need a really good reason to leave, which I don't see.

All else being equal, the career potential at UAL is greater, as is the potential for disaster. Stability at SWA is pretty much a given. I don't think they've ever closed a domicile and the only things that'll be left after a nuclear war are roaches the size of footballs and Southwest Airlines.