Dorno,
Coverage wise, this is what I see:
Oshkosh: Sprint is the strongest, the rest are all pretty good.
Mountain: Verizon and T-Mo are the strongest. AT&T is a clear 3rd and Sprint is dead last. But, this appears to be the sticks, so they might all suck anyways.
Then I have independent and recent data for:
Madison: Verizon is best, AT&T close behind. T-Mobile and Sprint are decent.
Milawaukee: AT&T is best, Verizon is close behind. T-Mobile and Sprint are decent.
My thought is this... you can go with any carrier IF you make sure that your plan includes roaming. So, if you're outside of AT&T's network you can use T-Mobiles, or outside of Sprint's you can use Verizon.
I'll pull up the best plans for you on AT&T, Sprint, and T-Mobile. I think we did Verizon before, and they're always pricey as heck also. Unfortunately, you're data usage is probably going to end up sticking you with an unlimited calls/texts plan which you don't actually need. Please keep in mind these prices do not include your local taxes and fees.
AT&T: Red Pocket Mobile: $59.99 for unlimited calls/texts, 2 GB of data. Roaming is included and free. AT&T's HSPA+21 is included, so expect about 5-6 MBps download speeds. If you don't like them, H20 Wireless has the exact same plan for $60.
T-Mobile: 2 good options here, and it'll really come down to what you want with data speeds. GoSmart Mobile (owned by T-Mo) is the cheapest. $45 for unlimited calls/texts + 5 GB of 3G data (meaning about 1 MBps download speeds). And Solavei, $49 for unlimited calls/texts and 4GB of data at HSPA+42 speeds (about 10-14 MBps download speeds). I use Solavei myself and haven't had any issues. If you're interest in them, PM me, and I can send you a SIM card for them for free (they're usually $9).
NOTE: I would personally recommend going with one of the above for 1 reason... you can get any unlocked GSM phone and use it on any and all of these. If you run into an issue or aren't seeing the coverage you like, you can just swap the SIM card and try another network. If you go with Sprint or Verizon, your phone locks you in and you've lost the ability to jump around. I highly recommend the Nexus 4 as it is still the best bang for your buck for a phone. And it has all 5 radios for both GSM networks
Sprint: Looking at the results... I say skip it. Unless you want a Galaxy S2 as your phone... the offering aren't great and they're all over $50.