I wish I could do a 1/1 comparison of xFrog trees and Speedtree trees, just to see which more closely approximate realism.
I tried the Speedtree demo once, but models saved in the demo are missing every 5th face cell, and the effect is so jarring that I don't feel like I could ever make a true evaluation of it. I suspect a lot of other folks are sticking the xFrog for the same reason.