Board Thread:Naruto Discussions/@comment-30381420-20161031234712/@comment-734582-20161101134441

GreatestSin wrote: i already said that it is sure that more eyes = more power, but the thing with madara getting 4 times more while other 2 times and in sasukes case it is a unknown factor, it simply seems to contradict each other in the aspect of "how much power one gets with a extra eye"... Previous users of Madara's Rinnegan did not actually own the eye. Nagato and Obito both did not use Limbo. So comparisons there are impossible. Secondly, if Madara had 2 Limbo clones with dual Rinnegan he would have no synergetic power from having both eyes. Only by having Four does he actually have greater power.

I recognize that it may seem like mathematical manipulation, but the power of one eye is 1/4th the power of two eyes, even though two eyes have double their potential. The hidden factor is the extra eye: One eye has 1/4th the power, the second eye has 1/4th the power (so together 1/2) and a factor 2 from synergy.

Although Obito's MS only doubled in speed (and did not fourfold), remember that it also grants Susanoo when both are present and thus Susanoo represents the hidden "synergy" whereas in Madara's case the synergy is in the greater use of the special power.