As jerseyfinn said, where you live is a big factor. Living in the PHX area and traveling regularly for business to Southern California, the Bay Area, the Northeast (BOS, NYC, and DC), and Florida (FLL/MIA and TPA), HP always was a perfect fit for me, and so now US fills that role. Plus now with the merger, when traveling up and down the East Coast (shuttle trips within the Northeast) and Northeast to/from Florida, I can concentrate EQMs in one program. So, the merger of HP and US really works well for my travel.

Neither UA or AA are anywhere near as attractive alternatives out of PHX. I'm not a fan of Ted, nor do I want to connect in DEN, ORD or DFW to get everywhere. I like the virtually hourly service HP/US provides from PHX to every other West Coast city, and I like non-stops from PHX to nearly every East Coast city.