We just returned from a cross-country six-month trip. We have Sprint phones and Verizon data pack. We had Verizon more often than Sprint, but had coverage in any areas near civilization, generally. We often lost it on outlying areas, but often had it in national and state parks -- most often during this entire trip, even when we lost it 'boonie-traveling' be got it back at some point in the day unless we were very boonie overnight.
The middle and west states - Nevada, Utah, Arizona, Texas, Oklahoma, Wyoming, Montana, Kansas, Dakotas had less service areas than most eastern states.
During this entire trip, we never got to the point of 'missing it' when we didn't have it. Because, soon enough, you move around and have it again.
It appears to us, Verizon has more coverage than Sprint - a lot, actually in the west especially.