Iphone 4 VS. Sprint HTC Evo 4?

I’m thinking of buying a new phone, and signing up a new two-years contract. I need two fully detailed-comparisons between iphone 4 and HTC Evo 4 in terms of the plans and what each plan includes and their monthly charges. What are the pro’s and the con’s of both devices?
I know that, at the moment, only Sprint provides 4G internet, while AT&T doesn’t. Is it worth switching to Sprint just for this feature, How wide is their 4G coverage in the states? esp. in St. Louis, MO?
Please don’t forget to include those (***) in-between-the-lines limitations that each provider has.

Many thanks.