Where are you chasing typically? I had Sprint for a time until I could afford to get Verizon again. Along most interstates, you're in good shape unless you're in parts of Dixie or getting into West Texas or the Rockies states. Off the interstate is where things get iffy. In some areas, especially in states like Iowa, Nebraska, and parts of Kansas where US Cellular has a large number of towers, Sprint users are allowed to get full speed data off of US Cellular towers when they don't have Sprint service. Outside of those areas though, Sprint simply does not have good rural coverage on their own once you're away from the interstates.
I know a few chasers who have Sprint as their primary service, and use a prepaid hotspot from either AT&T or Verizon to ensure they have data while chasing. The primary major hole with Verizon is western parts of Illinois (which AT&T generally covers fairly well), and for AT&T there are fairly large holes in the Northern Plains (which Verizon covers well). Other than that, data coverage is fairly similar between the two.