Ahh, that's not a bad argument. The Sage, however, was near-death when he gave his abilities to his sons. They are not nearly as powerful as they could have been, and if they were as powerful as they could have been they would have represented only half of the sage's power (each). The way I see the difference between his sons and Hashirama/Madara, however, is that they are two levels above Hashirama and Madara. Say, the difference between Edo Tensei Madara with interchangeable Rinnegan/Sharingan and EMS Madara that fought Hashirama. I still can't see them winning, even if the Sage's son with the eyes subdues the Juubi (I don't think Madara can do this, so I chose him), the Sage can still take them. The manga doesn't imply that he was even hurt after his battle with the Juubi.
I wasn't aware the Sons were ever given power by the Sage, are they not at full power for this match? Even if they are, I do agree that even with half the Sage's power each they'd be no match even against a non-Juubi powered Sage. The Sage's combat abilities are unspecified, but can be assumed to be vastly superior even to both his sons working together. He has almost complete understanding of the workings of ninjutsu.
(I say this because he is apparently the inventor of ninjutsu as well as being in posession of both the Rinnegan and practically unlimited chakra he must have a
pretty thorough understanding by now. But he probably hasn't discovered the extremes of yin-yang manipulations such as complex genjutsu or the Nara shadow techs. Also, Kekkei Genkai elemental hybrids and the Kekkei Touta can be assumed to be beyond him.)
We don't know much about his taijutsu capabilities, but I'm willing to assume he is less skilled than both Hashirama and Madara, pretty much because of upbringing. The Sage was a monk before his time to shine arrived, (probably not a martial monk) and advanced taijutsu capabilities are likely redundant in a battle against the Juubi, or even in the chaotic era of roving scavengers left in its wake, at least for a ninjutsu-master on the level of the Sage.
Madara and Hashirama, however, have been trained practically from birth in such matters, and are the result of unknown generations in which an incapable fighter was a dead man. Their Bloodlines both grant them advantages the Sage doesn't have in such areas (Rinnegan was never stated to improve taijutsu, and even the Senju-originator's body pales in comparison to Hashi's healing trick) though his stamina is likely far beyond them.
I see EMS Madara and Hashi as roughly equal to the Sons purely on the basis of combat experience (the Sage, being a former monk, probably didn't train his kids from birth in the same way as Hashy and Maddy), though their bloodline gifts are inferior. However, the Uchiha at least have had a long time in decifering the secrets of the Sharingan and Hashy appears to be a natural genius when it comes to Mokuton, so the younger duo can't be too far behind in pure potency of their bloodline.
Actually now I think on it, the Sage likely WASN'T injured in the battle with the Juubi. Reason being that any injury caused by the Juubi would be so massive it would probably instantly kill him.
You've gone and made me unsure who would win....
