Tobirama wins this high diff
--With tobirama having an edo body on his disposal means that he can use GKF to bust all of itachis susanooo variants bar V4 which still takes damage from the attack
--Itachis offense isnt cutting it here either, not when tobirama evades all of itachis attacks through FTG, and with sensing and intel on genjutsu, means that him getting caught under it, is also unlikely
--Tobirama not being able to properly breach V4 isnt a problem for him, since he has the means here to teleport itachi out of his susanoo and leave him defenseless, allowing tobirama to mark him and finish him off