On the Xcharger meth will strip the coating off the rotors. The only way to spray it is before the rotors. On a centrufigal SC you won't have that problem and get the benefit of meth's cooling as well as octane boost. The only issue is that you have to worry about running out of fluid, or the fluid not coming on when needed - the intercooler doesn't have that problem.

And this is what the rotors on the Xcharger look like with meth. I took these pictures when I upgraded a friend's car to the Xtreme.