Mancini did good to get us some title, but as we saw with last few games, Supercoppa, win in Milan derby & Coppa Italia was all he could do. I respect him for those achievments and bashing Juventus, but I think he can't take us to new levels. He is no managerial genius. Zenga has passion towards Inter and it would keep him up 24 hours before a big games thinking about the tactics and stuff. And I would trust him, like most of the Interistis would. It would be nice to have one of our own in charge! He'd know what's best for Inter, not for some of his personal friends. And he's managerial career has been really decent up to this point too. Those ex-players(fans) usually do very good in manager position.
Though, my second option would be Luciano Spalatti. He has proved himself to be one of the best managers that in the planet at the moment. Hiddink & Benitez wouldn't be bad choices either.