First off, the thing is big, like /thick/. And when I played with it, it didn't seem very responsive. The two screen bit was really cool though, and was really fun to play with. Dunno how rootable it is.
I have an inspire, which is close to the evo I'm told. And I love it, best phone I've ever used.
Frankly, they're both running android so no matter what you go with you're going to love it. Go to the sprint store and check out which you like better. Or Phonescoop the reviews.