I'm honestly not convinced that there are huge differences between the big legacy US carriers. Or, at any rate, your experience is just as much dictated by how busy their hubs are, whether your common routes are non-stop (as many of mine are with United), whether you're tending to fly in the winter in northern climates, etc.
I'm sure I would have absolutely no problem collecting a long litany of horror stories about every major US airline from among my Facebook friends with status.
So I go with United for size of route system and frequency of flights at my home airport and get enough miles to have status which does help. (Alternatively, for one shorter route where United doesn't have a non-stop, I usually fly JetBlue which IMO is one of the better bets in the absence of status.)