Pain based on feats. With so little Suiton feats in an area with so much dust, I don't see him being able to produce any powerful water techniques that could threaten any of the bodies. Tobirama is arguably faster, but the versatility and coordinative ability of the Paths will overwhelm him. Gravity control can repel his kunai and thus disrupt Hiraishin, which is his biggest asset. He has no way to counter animal summon spam.
Hopefully Tobirama invented the art of opening the eight gates, and thus can release all gates for some real firepower.
We haven't seen much but we know a lot. He beat Izuna who was was equal to pre Rinnegan Madara who already is stronger than Pain. He was the foremost water jutsu user and he created FTG and Edo Tensei. We might not have great fears on panel but thats still a lot. Even if Pain were to win, low difficulty might be a bit much. Naruto and Jiraiya put up heavy fights, Naruto eeking out a win barely due to a few factors.
Note that MS Madara is not EMS Madara. Although its not impossible MS Madara > Pain although it's hard to see.