I can't speak about the iPhone with any personal experience. What I can say is that the issues you should look at are which wireless network you want to be on, what coverage those networks provide in your area, etc. Personally, I've had the best success with Verizon - I even had partial coverage on Vinalhaven, with the closest tower being back on the mainland.
I also encourage you to think about the impact of choosing the newest technology for something that _just has to work_, given your profession. I am on a FEMA US&R team, and have found that Motorola makes some rock-solid phones which work and transmit when nothing else does, and hold a charge longer in adverse conditions. Again, something to consider. Having said that, the Razr is not a high-tech phone like the iPhone, it is not really going to give you the options you have with a internet device like Apple's iPhone.