GSP wins fights because he is bigger, stronger, etc...
But he certainly won't be bigger and stronger than Anderson, I don't see him having better technique anywhere.
A very tough fight, and I don't see GSP being nearly as impressive lately to even challenge Anderson.
GSP has gone to the end of the 4th with a tiny out of shape BJ, and had vasoline on his body, before that he went to a decision with Fitch, hell, in the rematch Matt Serra almost made the third round.
He just isn't walking through guys like Anderson is.
Anderson has walked through everybody he has fought in the UFC, minus a hickup of getting mounted by Lutter and a little boring Cote.
Either way, I just don't see GSP performing on Anderson's level