This doesn't really answer your question, but for what it's worth, I've been disappointed with the Smartwool T- and zip-T. I found that the wool T-shirt got much clammier than synthetics in warm weather, and took a while to dry. Obviously, much better than cotton, though.

My zip-T developed several small holes on the first trip...maybe the moth damage another poster mentioned. I'm pretty sure it didn't get snagged on anything.