umm, its only because he can block kirin, but if sasuke had knew those details, things would have been different, because you do realize he plan the whole battle even broke itachi genjutsu.
The bottom line is, Sasuke and Naruto are kishi most fav character so as of now i can't put sasuke or naruto vs anyone because they will win no matter what. and if it seems like they lost a fight, notices how kishi always make something interfering in the fight.
Sasuke ms vs itachi is nonsense anyways because sasuke fought itachi without Ms and did very well. If sasuke indeed had ms at the time with 100% completion of sasunoo the fight would have ended in a draw or sasuke would come on top simply because he can break gen jutsu, everything else cancel out each other.
However. the swords and mirror itachi has i fear wouldn't be easy to catch sasuke for several reasons.
1. i high doubt he can just use it when he wants because i think their is a chakra cost in using them.(everything in Naruto has a cost)
2.( catching Sasuke is another thing because sasuke speed is 1 second beside Itachi's, however sasuke has the abilities to predict itachi move and counter it, just like itachi has the battle to. (example would be Itachi jumping over his clown to throw a shuriken, and sasuke seen that and did his counter. he also threw out strings invisible to the naked eye and caught itachi legs with it.
(this move orochimaru stated is called Sharingon triple frontal attack, something like that.)
The way i see it is they will draw.
Itachi ms vs sasuke =itachi
ms sasuke vs ms itachi=draw
EMS sasuke vs itachi ms= undetermined