Unlike Minato, Tobirama doesn't use a marked kunai tactic for FTG, so this is in Itachi's advantage. He could do same as he did to Sasuke, by covering the location by 360 of Amatersu. [
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] Itachi, alive at the time, covered half of it despite having Tsukuyomi and 1st Amatersu consuming his Chakra and health. Granted by the Edo Tensei unlimited Chakra and stamina, it isn't a case and the Uchiha can spam Amatersu at a much larger rate. A 360 Amatersu would prevent Tobirama from escaping outside the area, leaving him in short to mid range battle between him and Itachi, which the latter would prevail with Sharingan and Susanoo CQC pulverising the Senju.
Itachi wins mid difficulty.