As a non-elite the is zero difference in coach service for all the majors, it's such a miniscule difference--except for Jetblue or Song--their products come close to some airline's F experience (NW and US come to mind).

As an elite member there's a minor difference as you might get a UA E+ seat, which by teh way has the saem pitch and smaller width of a Jetblue seat behind row 12....so go figure.

I do agree that airline travel is now as commoditized as ever.