It obviously depends on your personal experience. In the Phoenix area, I have had excellent service with AT&T and don't see many/any of the problems that I hear those i other areas complain about. A couple of my kids have VZW, and are likewise satisfied with their coverage.
Ultimately, you have to choose based on your experience. Do you have any friends/co-workers who are with VZW? Do they live/travel/work in the area where you do? Find someone who has VZW and pick their brain about their service/coverage, etc., maybe take a ride with them along your daily route to see what works/doesn't work.
VZW has certainly stepped up their game when it comes to phone selection lately.