Basically, there are two parts to a ninja's skill: Body, and Eyes
Theory: SO6P had the strongest body and eyes, Indra (Madara) had strong eyes but not as strong as his father, Asura (Hashirama) had a strong body but not as strong as his father, However when You combine Asura and Indra's chakra, both the eyes and body evolve EVEN further because of EMERGENT Properties, so that they eyes are stronger than Indra's (EMS -> Rinnegan) and the body is stronger than Asura's (Strong Body -> Even stronger body)
The Sage had powerful eyes (rinnegan) , and a powerful body (strong healing and chakra) which is what made him so strong.
The Senju excelled at Body
The Uchiha excelled at Eyes
When Madara combined Asura's and Indra's chakra, he awakened the sage's eyes. But therefore he should've also awakened the sage's body!
But we should define what the sage's body was like. It was probably just like Hashiram's body but with a higher healing factor and higher chakra levels, however there are no AESTHETIC differences, meaning it's just a normal body, it isn't any more muscular or different colores unlike the rinnegan which looks different from Indra's eyes.
Something inportant to note is that this isn't really focused on because the Body is much more passive, it doesn't change form or shape unlike the eyes which get a new pattern (EMS -> Rinnegan) but we know Madara had it because of everything above.
This means that Madara not only had stronger eyes than Hashirama (by default) he also had a stronger body (and therefore more chakra than Hashirama) after absorbing his cells, i.e., he was more durable (in terms of being able to heal on the level of SO6P) and had more chakra than Hashirama as well (Madara's total chakra was equal to the SO6P before absorbin the Juubi)
This makes sense since Madara's eyes didn't stay EMS, they evolved to the sage of six paths level, so it is natural that his body would evolve the same way.
What does this mean? Edo Madara should've been able to make a CT the size of the moon and should've had much MUCH higher chakra levels than Edo Hashirama.
Why didn't this happen you ask?
Because of Madara's only weakness (aside from Kaguya): Plot no Jutsu
Basically the point of this thread was to prove that Combining Asura + Indra's chakra results in EMERGENT properties. The abilites of the person are not simply INDRA + ASURA, they are much higher, they are on the level of the SAGE of Six Paths, Combining Asura + Indra's chakra are much more like multiplying their powers than just simply adding them.
Thus, Madara's pre-jin chakra levels are not simply EMS Madara + Hashirama's chakra level, they are infact much higher. '