I'm based in PHX so I guess I'm biased, but having connected through DFW and LAX many times post merger...PHX is way better. If I were flying on AA to somewhere out west and I had to make a connection, I would gladly take up to an 1 hour difference in total travel time to go through PHX. I fly through DFW at least twice a month and I am delayed almost 1/2 of the time. LAX you may have to catch the bus... I never connect here but PHX is super connection friendly as the two gates that are farthest apart are less than a 10 minute walk. The only advantage I would give LAX and DFW domestically is their Admirals club...the one's in PHX can get crowded.