Sasuke wins this easily. Itachi is a non factor. Nothing in his arsenal will do anything to Sasuke. Genjutsu gets seen through, Ninjutsu and Taijutsu blocked by Susano'o, and Totsuka has no feat or hype of being able to get past Susano'o. Tobirama is in the same boat. Warping Susano'o isn't going to happen because he needs to touch it for that. Sasuke can coat the entirety of his Susano'o in flaming spikes. Touching it is suicide. Tobirama will get taken out easily by Susano'o simply because his FTG isn't versatile enough to allow him to evade. Itachi will be on the defensive the entire fight, and he will have to have Susano'o active constantly or a sword swing or arrow will end him. Eventually he will get exhausted and won't be able to keep up Susano'o anymore, and that is when Sasuke wins. I don't see Sasuke taking this with anything more than mid difficulty.