My best friend is a commercial airline pilot and won't use anything but Verizon. Due to his occupation, and the related travel, he can test coverage better than anyone I know. I don't recall the last time he tried AT&T, but it was surprising how many areas were not covered, and these included areas that were very well populated. Unfortunately, Verizon knows what they have and there is a premium to be paid for it.
I know plenty of people that "make do" with the others, particularly AT&T and Sprint. My wife is on a T-Mobile pay-as-you-go plan. Data is horrible west of Grand Rapids, and just spotty altogether, but it is cheap. A coworker is less than thrilled with Boost, but now I can't remember if it coverage is lacking everywhere or just at their cabin.