There are a lot of issues to consider. I have a Virgin Mobile phone - similar to a tracphone, I pay for minutes I use, and I don't use nearly as many as you do. It will send text, which I consider a necessity for emergencies, as texts often go through when you can't get a dial tone. I don't check email with it, but sending text messages to my wife is handy more often than I'd have expected. It has a camera, and I wish it had video, too. Plain vanilla phone.
My wife used to have a Palm phone of some kind (not a PDA combo). Now she has an iPhone. When we're in San Francisco, she can use it to find parking spaces (some iPhone app or other). When we're with friends, she can use it to get directions when somebody's husband won't ask (our cars have navigation built in). It has Safari, a real Web browser; her Palm wasn't worth the aggravation for checking something on the Web. She can google the name of a restaurant, get it's number and call for reservations on the spot where ever we are. The apps available for the iPhone are astounding; many are free, many are a few bucks. She can photo a SKU tag and compare prices in the store, with Amazon. If the store has a Web presence, she can compare the in store price with online, order it online if cheaper and have it delivered "to the store" with free shipping and pick it up while we're there at the online price. :->
For some reason the iPhone is much more useable than her Palm phone. She has three screens full of additional apps that I don't have a clue about, but which she uses for stuff.
I'm happy with my Virgin Mobile, and she's much happier with her iPhone.