The reason the sage would win is because he had was both Senju and Uchiha, and he could use Izanagi whenever he wanted without losing an eye, and he was the host of the Jubi which = unlimited chakra.
It isn't because he had two rinnegans, it's because he could do so much more than Madara could and possessed the full power of both senju and uchiha blood plus infinite chakra.
I saw you on another thread saying that it was stupid for Madara to not use both rinnegans but they don't have the same abilities, the sage had them because of his blood and the fact that he could do practically whatever he wanted with Izanagi.