It would be a shouting match. Hannity would be constantly trying to shout him down when he knows he's out debating him or dropping truth bombs his viewers won't like and he'd smugly cut to adverts every time he's losing it.
Except Hannity wouldn't even embark on the interview since he himself is linked to Cohen and he's probably wetting his pants at the thought of Avenatti dropping some new information about him and his association with Cohen LIVE on Hannity.