Pretty sure that match used alive Itachi, which at the time was Part 1 Itachi. Regardless, alive Itachi doesn't fare that much better, in my opinion. The Six Paths of Pain are too diverse with their abilities, and Nagato already has prior intel about Itachi, while Itachi doesn't know much about Pain's abilities in comparison, or at least not that I'm aware of.
The Six Paths of Pain and their shared vision give them a tremendous advantage. Pain can absorb the Amaterasu using the Petra Path, can use multiple summons with the Animal Path, and the Deva Path can push Itachi out of the Susanoo if he chooses to use it. Even if Itachi manages to take down one of them using his genjutsu, the Naraka Path will fix them, and because the Pains can attack from multiple directions, the Yata Mirror won't be able to nullify all the attacks. Itachi doesn't have any answers for the Chibaku Tensei, either. Itachi's stamina isn't the best, since even using the Amaterasu once was draining for him, and he could only use the Mangekyo Sharingan three times a day before needing to rest.
