The Hokages barely have any feats.
Yamamoto stomps. Basically he's the worst opponent for both of them simply because he's going to burn down all of Hashirama's trees and he'll make it so hot that Tobirama's water techniques will all evaporate.
Even Hitsugaya, who was pretty far away, said that he couldn't use his Zanpakuto anymore simply because Yamamoto activated his bankai.
Yamamoto wins by default... Too fast for the both of them and beats them in strength too! Also can avoid being caught in Hashi's Mokuton through air walking! Bankai isn't really necessary either! Perhaps if speed was equal then this fight would be a lot more interesting!
@CallmeBrent: @ohgodwhy said:
@CallmeBrent: Because Hashirama would get raped by Yamamoto too!!
You have to remember Hashirama beat normal Madara, not EDO/Rinnegan Madara who can use all the ridiculous jutsus because he has an infinte chakra supply.
Edited a bit.