..I have been with Sprint since the late 90's. Reliability hasn't been an issue, but the sound quality is. I recently heard that might be because they tend to stretch their cell tower network pretty thin.
...My father got an iPhone 5 last year and switched from Sprint to Verizon. He is very happy with them and the phone. I was leaning towards the iPhone simply because of the fact that my 68 year-old father figured it out pretty quickly. That means there's hope for me.
...My brother, however, is a technophile and he keeps pushing the LG G4. He says it works well across all the carriers, has a ton of great apps and allows you to quickly (and relatively inexpensively) change the battery on your own if it runs down. It sounds a little over my head, but I'm not telling him that. I can't let my little brother get a swelled head by telling him that he's smarter than me.