Both the Sprint Touch and the Diamond have EVDO, which is Sprint's (or rather CDMA networks) version of 3G.
I personally love the Touch. The BB is a great choice if you text a lot, but you say that you don't. I have the GSM Diamond and haven't seen the Sprint version yet, which should be out in a few weeks. So I can't tell you much about their particular flavor of the Diamond. But it will run the same software as the GSM version. That software is very pretty looking and has a lot of wow-factor, though it may not actually add that much usability over the original TouchFLO found on the Touch. For the Diamond, I'd say you really have to use one and see how the user experience suits you-- you may love it, or you may not. The Diamond, since it has a lot of features and is new, will likely cost more than the Curve or Touch.