I have an iPhone 4 and serves me well. At the same time my carrier has excellent service and coverage in the area I work in. Service veries throught out country. It be best to chat with locals in your area. If you do get an iPhone, I have a few apps I highly recommend.
My favorite app is GoodReader. It can easily handle large .pdf files with no problems. I have catalogs, drawings, manuals at my finger tips that I can download offline of from emails. Bookmarks transfer over so none are loss plus you can add them on your phone. Drawings suck on the small screen but its handy for reference.
I have the app on my iPad too at no cost is another reason I went with iPhone.