I had AT&T in Phoenix AZ, and then in Manasass VA, and when I moved back to Phoenix I gave T-mobile a shot. They had 21-day trial thing so I got a phone and drove all over the place, especially checking places I knew I would likely be, checking reception and such, and overall the quality beat AT&T.

It may be , though, that what works best depends on the particular region. Still happy with their customer support; they helped me in assorted ways and it was quite pleasant.