If you stop and think about the two choices you have presented, the logical (non-technical) choice is Verizon. Verizon has over 92 million subs, Sprint has 48 million. Verizon is growing while Sprint continues to suffer from some of the worst customer retention in the industry. BTW, I am a Sprint customer because years ago Nextel was a good service in Door County so I went to Nextel, then moved to Sprint with the acquisition of Nextel.
Anyway, given the option to start over and do so for the UP I would pick Verizon over all carriers. The CDMA service will "stretch" a bit further then AT&T's GSM service (my opinion sort of half based on fact) And, since you have limited your choice to the two CDMA carriers, by logic you can expect Verizon to be investing more in their network in remote areas, solely due to size of budget.
If you look at coverage maps you will see that in areas like the UP where people "drive through" coverage is built along the highways. That is a core strategy of network expansion...cover the drive-throughs first so the existing traveling customers have service, then expand out for local customers. Over the long term one would expect Verizon, with twice as many subs as Sprint would be more inclined to expand local service in Da Yoop just 'cuz they have more money, more people, more tower leases, and more trucks.
Since you will have to sign a 2 year contract one should expect that in 2 years the Verizon network will have grown in Da Yoop while the Sprint network will probably remain static. Also, I have been unable to get an HTC EVO, it has been sold out online and at Best Buy online since end of June. I will be ordering the Samsung Epic tomorrow from Sprint. The EVO shortage is apparently due to a shortage of screens, oddly enough they are made by Samsung!
Sorry for being so wordy, but in 2 years you will be happier with Verizon IMHO.