I'm kinda tired of all the fanboys here, so let's look at the facts.
Throughout the story Sasuke has proved to be VERY confident, in fact border-line arrogant about his powers. The likelihood of him actually being genuinely scared of Tobirama (Even if Tobirama was stronger than Sasuke) Is incredibly low.
Tobirama has also proved to be extremely aggressive when it comes to threats on the leaf village. He was almost guaranteed to at least TRY to attack Sasuke.
And lastly, although Tobirama is a very strong Shinobi, It was Hashirama arousing his extremely powerful chakra to let his brother know he does not approve of unnecessary violence in his presence, that caused the ruptures in the building. It was not Tobirama's doing. (Or at the very least it was a combination of the two of them)
And as for Suigetsu "melting", It was a visual queue to describe just how afraid Suigetsu was. After all, if fighting DID break out, Team Sasuke would be fighting the strongest Shinobi in the world besides the Sage Of Six Paths. (Hashirama) It was not Tobirama stealing water from him to prepare for an attack.
Also I think you should all get off your respective Waifu's nutsacks. Yeah Sasuke is strong, Yeah Tobirama is cool. But if or until they actually fight, you can not say "Sasuke would win Lolz" or "Tobi would mop da floor with sasuke ROFL".
Also wheres the love for First Hokage? He essentially told them both to sit the **** down before he starts wrecking peoples days.