We chose Sprint because of the plans available. Got sick of going over our minutes with our last company, so the plan where it automatically bumps you up to the next rate plan instead of sending you hundreds of dollars over is great. We know that no matter what, our phone bill will only be $X.
The sales people are energetic and helpful, quick to help, no standing around waiting. If you hold out on them a bit, they will likely give you a phone for free if you choose one that was under $50 anyway.
PROS: Great plans, clean store, helpful personnel.