Since the removal of first class,
, I always go for the exit row. Yes, it takes you a few extra minutes to get off the plane, but I always gate-check a roll-a-board and it takes a few minutes for ground personnel to get all the bags plane-side or up into the jetway, so the timing works out about perfect. There is substantial extra legroom in the exit rows of many of the planes, which obviously matters if you're going to be sitting there for any length of time. Granted, PHX-LAS is a wonderfully short flight, but delays happen, so it might be worth it.