I voted for a draw. I mean it's undeniable that Itachi is a true master with the Sharingan beyond most other Uchiha. It is also undeniable that Hiruzen was the definition of "God this mother F***** is strong" in and out of his prime. Hiruzen is a master of the shinobi arts, and I would say even beyond that of Itachi, although Itachi's mastery of his unique dojutsu gives him an overwhelming amount of power. It's safe to assume that Hiruzen is fast, fraily strong, and had higher stamina then Itachi in his prime (he may have had more then Itachi when he was an old fart idk). However we don't know if he's fast enough to get away from Ama, we don't know if he has a method to get rid of Susanoo. With Enma at his side Tsukuyomi could be useless, and as seen with him defending against Tobirama's genjutsu I assume standard genjutsu won't work on him even without enma. Itachi has fairly strong ninjutsu without his MS but I wouldn't compare that to his MS jutsu, he also has great taijutsu, although I'm not sure that is a match for Hiruzen either. Itachi is probably going to have to rely on his MS and the only problem I see with that for Hiruzen would be Ama and Susanoo, although I'm not sure if he had some ways to deal with it. Hiruzen in his prime I see besting everything Itachi has to throw at him with the exception of those two techniques so I'm not sure. That's why I said a draw.