I just dont see how being alive is a powerup. In his edo tensei body he could regenerate and shit, he shoulda waited till after he defeated Hashi and a few others to come back alive, Obito wasnt gunna go anywhere
Here are my thoughts.
1. The weakest 'power up' is adrenaline and survival. As an immortal Edo, you can afford to get hit. However, as a human you can't. Meaning that you have the adrenaline pumping through you giving you that extra survival rush.
2. Absorbing failed beasts. I know it sounds far fetched. But this option is now available to Madara. As someone with Sage Knowledge and having awakened the Rinnegan. He likely has a method more practical than the Gedo Statue method... Or the knowledge to use it more efficiently.
3. God Tree Fruit. I'm still banking in the idea that this fruit is going to make a debut. And as a Human, Madara can eat it to obtain godly power.
4. Tobirama mentioned that Edo Tensei didn't give them full power even now. I know that this might be a split boost considering that just after using it he'd soon be losing chakra and basically getting weaker. However, considering Naruto, Sasuke, and the alliance are all still going strong. I'd say he's not at an immediate chakra drain risk. Furthermore, if he does intend to absorb beasts... The larger that supply is. Having all 9 basically gives him close to infinite chakra. Or enough to the point it doesn't matter.
All in all I don't think being human gives him more strength... I think it's an OPPORTUNITY to gain more power.