Where I live, AT&T is dramatically better than Sprint.
I'm on the 450 minute/month plan, with unlimited texting, unlimited mobile to any mobile, unlimited nights and weekends, 3GB of data, and the premium insurance plan. I pay just over $100/month when all taxes and fees are considered.
I've never had a problem with service, except in very urban areas, i.e., large cities.
I'd compare plans for both and ask people in your area what service they have and whether or not they like it. I think it all depends on geographic location to be honest.