I have a G20 as well as the super. In ballistic testing the 45 Super leaves bigger holes and does more damage. I like them both. The gun is intended for hunting deer and hogs so as long as we are talking about thin skinned game the .45 Super wins.
The gun is built with one of the old discontinued "Heavy" slides. 5oz heavier than a G41 slide and you can tell it. With the 6" barrel and a 24lbs spring the slide is slowed down drastically. I have tried buffers in Glocks but they destroy them. I am sure you know that the exit from the 6" barrel being later coupled with the Heavy and the spring completely prevents frame battering. If I build another one it will be on a G21 with a KKM barrel and comp.
I have a G21 converted to .460 Rowland. It is a whole different ball of wax. Really fun gun.