It depends on where you live and where you go, I've had them all Verizon, t mobile, at&t, cricket, sprint and others I can't remember but now I have boost mobile and I love it, boost is on sprints network and towers.
The other answer is correct - Boost Mobile runs on Sprint's network, so depending on where you are, you might or might not get good service. For me personally, the order of good service goes as follows: AT&T > T-Mobile > Verizon > Sprint.