As others have pointed out, this really is a pointless argument because it all depends on where you live. I live in the mountains of Western of North Carolina. Most cell service here is crap but Verizon is the best, plus Verizon is the only LTE option, with AT&T you only get 3G. My sister lives in West Palm Beach. While I had LTE down there, service was spotty. When she moved there, she had Verizon and had to switch. AT&T is bad there too, she has Sprint and in West Palm it is awesome. When she comes home to Asheville, she has very spotty service.
It is all a matter of where you live, there is no right or wrong answer for everyone!