Depends where you live and what you want to do. If you want to spend 30+ hrs in a hotel in a foreign city then DAL is probably for you.
If you want to spend no more than 4 days on the road and don't mind not flying legs longer than 6 hrs then SWA might be for you.
Long upgrade at SWA wasn't a consideration for me. I'll make very good money as a FO living in base. Don't really have a desire to spend 11 days on the road crossing the pond multiple times.