I honestly never understand these sorts of posts. The grass isn't greener anywhere else, and that's coming from an airline employee. I can't tell you how often I've heard pax's leaving us (UA) for Delta or AA, only to have my friend's who fly at those airlines say folks are leaving DL and AA for us. I honestly don't think on average, the service is any better or worse on any domestic carrier. Fly with the airline that is most convenient for you, and accept the fact that the experience will most likely be mediocre to occasionally good at best.