FYI, the regular Powergrip has organic on one side, but the same sintered iron as the Powergrip HD on the other. Both the regular Powergrip and the HD version use the same polysprung hub, and both use the same marcel style carrier as well.
I have a used dual friction regular Powergrip on the shelf, it has a couple years on it and both the iron and organic sides appear to have about the same amount of wear.