First of all, if he's to be sacked during the season (which seems very likely), we wouldn't have too many options. Of course, some would say that in this case we should just give him time until the end of the season, but I believe we're reaching a point where a caretaker would be a better option. Regardless, we have Mourinho and Allegri still available at this time, but I wouldn't want Mourinho. I'd take Allegri in a heartbeat if we could get him though.
If we'd have to wait until the summer, Benitez would be a very good option in my opinion and to a certain extent Rodgers, although the way he left Celtic showed just how disloyal he can be.
So in short, my first choice would be Allegri, followed by Benitez. This is the direct answer to your question. It's not up to me to pick the coach and there's no guarantee who we'll end up with.