Around Ontonagon proper, at&t has the best service. On the fringes (mass, green, white pine, rousssau, etc) it seems to be a dead heat with Verizon and at&t....one might work in a spot, move 10 feet and the other will work. I know Sprint and Nextel are the same company now...I think Nextel is useless in the Yoop...not sure if that means Sprint is too or not.
In those fringe areas, we do see smartphones do a bit better...marginal though. Almost the same affect if you stand on one leg on a full moon....sometimes you just can get a signal in the right place at the right time. New Verizon and at&t stuff going up last year and this coming year, i know at&t is slated to be done by late this year with quite a few.
Since iPhone and Verizon was mentioned, might take a look-see at this
http://www.bgr.com/2011/01/10/why-im-not-switching-to-the-verizon-iphone/ . No idea on the validity of the article but I do know that these sort of differences in platforms-etc can make a difference.
What we find...and what we ask customers to do...try a droid phone before you buy an iPhone. Everyone I personally know ends up taking and loving the droid phone. I sell both, so it is not a dig toward the iPhone...it is what we see-hear. I would at least kick the tires before I got one.