Sprint's coverage really only sucks when you're on an MVNO (Kroger, Virgin, Boost, etc) because those are locked to "Home Only".. When you are a Sprint customer you're allowed to roam for free on their SRP's networks - Verizon in most areas, but also many smaller CDMA carriers (like Pioneer Cellular, US Cellular, nTelos, etc). I had Sprint for 15 years, but I dropped them last year because they lost their SRP in my area so I became 100% roaming.. But what's funny is the mom and pop carrier I switched to (the former Sprint SRP) has nationwide outbound LTE roaming on Sprint (3G on Verizon). Go figure..
And yeah as far as the nearly identical coverage, several years ago the FCC mandated that carriers must allow colocation of other carriers on their transmitter sites. As a result, now each tower you see has transmitters for multiple carriers, and the signal propagation will be very similar among all carriers using the towers. Same goes if a carrier has leased a transmitter space on top of a building or water tower - if a landlord leases space to one carrier, he must lease to any other carrier as well, provided the space can support it.
bc sprint drives me to drink sometimes
