A Genjutsu battle just as it sounds like. Who do you think would trap the other in a Genjutsu? It can be any type of genjutsu they just can't use taijutsu or ninjutsu. Keke Ge kai is allowed. Who do you think takes this one?
Itachi showed alot of different forms of genjutsu and is known as a master of it, madara on another hand is not like this at all. So itachi would destroy madara here.
I personally think that they're at a draw. Sure Itachi knows a lot of genjutsu but who knows if Madara also knows those jutsus. They'll just stay at a stalemate