Itachi praised Madara for being the most powerful character in the Uchiha, so any attempt to claim Itachi wins is just crying for when character admits inferiority. Also, I don't see how Itachi can win here. Amatersu can be blocked by repelling Gunbai, which Madara can tell the build-up by the Sharingan. Even drained Sasuke can outrun it. If he ever uses Susanoo, he gets a death wish. His stamina only allows his usage of MS three times a day; beyond that, he dies. Simple as that. Madara would wreck him in CQC, and his Katon style dwarf Itachi's Katon. There is no comparison. Madara wins via outlast. Author portrays Madara the stronger and Itachi agrees with that.