I just noticed something else that is different about Madara's So6p form. On the back of his coat, he doesn't have the tomoe that connects to the rinnegan eye like obito did. That is how the real sage looked when they showed the flashback of him with the baby tailed beasts, and then when obito turned into juubito, he had a tomoe connected to the rinnegan design on his back. Now Madara turns into the juubi jin and he doesn't have it. Maybe because Obito had a sharingan it made a tomoe appear there? Madara only has the rinnegan so it wouldn't appear? I don't know, just thought it was strange. Maybe because madara has mostly all of the chakra from the tailed beasts unlike obito, who had less?
Every single difference between them is important. Nothing should go unrecognized. Lot of theories abound.