Nalbandian, Safin, Agassi, and Djoko are great at generating power on a rally/sitter ball with 2 HBH.
Federer, Wawrinka, Ree-chard, Haas, and Almagro are great with 1 HBH.
I voted equal but can see the argument for the 1 HBH as it is basically a longer lever and more flowing stroke. But, as good as all those 1 HBH are, I might take Nalbandian, Djoko and Safin to dispose of short balls better on the BH side. Heck, Djoko kills Nadal by stepping and hitting his 2 hander either hard up the line or hard CC.