He would need biased conditions (like better knowledge or good distance) to beat the stronger forms (like Finnegan Madara) but he can definitely beat them.
Can't Itachi bypass Madara's PS with his ethereal spiritual items, though?
Didn't IA Naruto outsmart 80+ age old experience and wisdom possessing Kakuzu? Also, didn't he have comparable reserves to KN0, and still lost due to Naruto's ingenious trickster strategy?
Yeah, that is a possibility that was never fleshed out - in the series. Seeing as Madara has impressive long range attacks, I believe we may not even reach the point where Itachi could pierce Madara with the Totsuka. I also don't believe that the Yata mirror can deflect any type of attack. Another thing is Madara's vast experience will prove much for Itachi to handle, in addition to his immense chakra prowess and great techniques.