I had Verizon and now have Sprint. Sprint is cheaper, $59.99 for unlimited data. Verizon was 79.99, I think.
I do live in the sticks so I agree with Viking, it is not as good out here. I would say a little better that Verizon coverage. If you live in the weeds, you need to have an antenna, my sprint card has a little flip up antenna and I have the external USB cable so I can move the modem around or leave it plugged directly into the PC. On Verizon, I just had a card so I had to hold the laptop near the window to get a signal. In cities, they were both good, so Sprint's lower price was a deciding factor. I think you can get discounts if you have cell phone accounts with them as well.
The one complaint I have with Sprint is the user interface sucks. Verizon's had a realtime graph that could show your signal strength and data rate. Sprint's just has those tiny bars like you see on a cell phone to show signal strength, and the data is just measured with a number