FWIW, I work in IT and am somewhat of a self-proclaimed mobile device whore.
There are no easy answers to your questions, however one thing I can say is that Nokia handsets are typically regarded in the industry as having some of the best and most reliable cellular radios of any manufacturer while, unfortunately, most modern Motorolas are the worst. Sony Ericsson puts out a decent device but often times have very sensitive cell radios that will jump around and not lock to a frequency. These are not my opinions rather somewhat acceptable truths from within the industry. Not necessary correct in all cases/models but a good general "rule of thumb".
Personally, as much as I *hate* their user interface, if I were moving to a rural area with shady cell coverage, I'd buy a Nokia. Can't recommend a specific device as that depends on what carrier you chose.
Speaking of: Out of all US cell providers, Verizon, Cingular (now AT&T as of today!!), and T-Mobile are on top.
Verizon is the only CDMA network of the three which, if this were a few years ago, I'd say go with hands down as CDMA had decent ability to cover broad-range distances *when* their dual-mode analog/digital handsets were still around. Perhaps that remains true for where you're moving, but to best of my knowledge they're digital-only in most markets which gives equally as poor results in poor coverage areas.
I would stay away from T-Mobile @ all costs. T-Mo and Cingular (ATT) are GSM providers. GSM runs on two different frequencies here in the US, 850MHz and 1900MHz. T-Mo ONLY uses the 1900 spectrum which, by all accounts, gives you less roaming capabilities in general. That being said, T-Mo *may* have the strongest signal presence where you're off to...
Here's what I'd do. Check this site (http://www.wirelessadvisor.com/
) and put in the ZIP of your destination. It will tell you what services AND frequencies for GSM are available that area. If you want to look at Cingular, check out their street-level maps here (http://www.cingular.com/coverageviewer/)
. While not always accurate, it can't hurt.
Lastly, most providers now have a 30 day trial period so use that to your full advantage. Sign up, pick a handset, try it out. If it sucks...bring it back within 30 days, rise and repeat!