Board Thread:Theories and Speculation/@comment-28252336-20160512015637/@comment-734582-20160512084309

Omnibender wrote: Like I said, Madara would not trade his Rinnegan for Tenseigan. Not to mention, he had one Limbo with one eye, but four Limbo clones with two eyes. Clearly, power is multiplicative with a set.

So as was said above, eyes are strongest when the same set is together. This is both true in Obito's interpretation (two people cooperating) and in Madara's interpretation (one person having both eyes)