All carriers employ partnerships for coverage expansion. Sprint owns boost so while boost uses some of sprint's older pcs towers it does not receive the full benefit of the sprint network. Virgin mobile is now owned by AT&T and is again on it's older towers. both have some advantage and disadvantages. mostly with after purchase support, and both are standard pre paid phones. they offer no warranty beyond a short return period, and no third party handset protection. you buy it, if you break it you buy it again.

Cricket as well uses partnerships to expand it's coverage and has a larger coverage area than virgin or boost. while the phone support is not the greatest since they have corporate owned store locations to provide support you can get the help you need face to face. also their phones have a 1 year warranty, and you can add handset protection to reduce replacement cost if anything happens to the phone. you will also find that with boost you do not receive the same quality in handsets as with cricket, and slower data speeds with lower limits to data usage.