I have 3 cell phones (none iphones), 2 t-mobile and 1 Verizon. I prefer t-mobile but I use it mainly in Chicago and travel the entire midwest area. Go to each providers site and compare coverage maps to see who has ya covered the best, if 2 are similar then I guess it's a plan debate.
http://www.verizonwireless.com/b2c/C...cm_ite=Roaming
http://www.wireless.att.com/coverage...k=1-006KVD-0-5
http://coverage.sprint.com/IMPACT.jsp?INTNAV=ATG:FT:Cov