I would recommend looking at the tower maps before taking the plunge especially if you are going to be in a rural area..
THIS LINK will take you to a interactive tower map.
You can see where the towers are for Verizon, ATT, Sprint and T-Mobile in relation to where the address you put in.
For my area, I have to drive 20 minutes south west to get close enough to Sprint or T mobile towers and there is only three towers.. We ended up on ATT because ATT has more towers (more coverage) in our area..
From what I have been able to figure out is the best coverage is between Verizon and ATT over all, T-mobile and Sprint coverage is more in large cities than rural..