Wow, OnPoint made a thread?
OT: Tobirama can win fairly easily. His Kage Bushin can number in the hundreds, meaning that Mū cannot end this by slashing Tobirama's throat, or atomising him via Jinton.
For range he can merely cover the surrounding area with water, and wait until Mū strikes. If Mū makes a pass at one of the clones, the Edo Zombies (as they have his chakra flowing through them) can be teleported to that area, where they can use Kibakufuda to end him.
Mū has no answer to Tobirama's Hirashin versatility. The nature of the technique means that wherever one Tobirama clone is, the rest can all amass there in a moment's notice.