From the moment they start out with Susanoo, the loser would be the one with the lowest stamina since their combat abilities won't be enough for either side to survive Susanoo techniques without Susanoo. Itachi despite being Edo would still lose. He needs more than 30% of his chakra to use MS techniques. Kabuto's edo tensei technique recovers Edo stamina when their chakra is 0, so basically a Edo can run low on stamina like Muu after he divided himself or Trollkage during Jockey Boy and in this case if Itachi is at 5% of his chakra for example, he couldn't use MS techniques, reason why he would lose. It was even hinted during their battle against Kabuto where Sasuke despite having Sharingan that rate chakra percentage was worrying if Itachi could still keep up Susanoo. EMS Sasuke on the other hand can spam EMS techniques like no tomorrow in the contrary of Itachi. While Sasuke has no sealing techniques, according to OP, Itachi can't regenerate, so he would get killed in the end