No, no clear winner. Generally every metro area has it's winners and losers. Sprint and T-Mobile have worked well here for me, for instance. Verizon is the only one I would think might have a slight edge, but I'm still not sure it's that compelling. When you're talking about no signal in a rural area, there's no guarantee it will be better with another provider unless you mean one specific rural area and can track down the exact network coverage for that spot. If you mean various areas, switching probably won't help.