From what I've read on the Hero and my experience with the TP2 I'd say that the latter is the better phone (TP2.) It has a bigger screen. If you look at the dimensions of the TP2 alongside the Hero you'll see that although the Hero lacks a hardware keyboard it's only slightly smaller and thinner that the TP2. For someone who is a heavy texter I think you'll really appreciate the spacious keyboard of the TP2 over anything onscreen. ... My 2.5 cents...
Here's a link to the post in the Hero thread where the two phones are shown side by side. This should help you make a decision.
http://forum.ppcgeeks.com/showthread...=77325&page=32