I've used t-mo, att and verizon here in the la/oc region. From my experience verizon and att have basically the same good coverage everywhere. Few noticeable exceptions are right on the beach-ocean were verizon is stronger and sometimes in very hilly areas one carrier is strong but on the flat la basin verizon and att are basically identical. Overall t-mo has slightly worse coverage and if you ever get out of the major city it falls off a cliff.