How is he much better than Ranieri?
I think both have different style about them (can't really compare they're track record cause both pretty much haven't won titles).
Ranieri is more of a cautious manager. He'll do whatever the owners will tell him to do (pretty much a weak character). I don't like his type and IMO you can't go far with him no matter how long he stays in the club.
Del neri takes more risks, a tough character (he benched Cassano last season even though he's the "star" of the team and they're main guy). Personally if i had to choose between the two i'll definitely pick Del neri over Ranieri.
Plus i really liked Del neri's Chievo team which was one of the best attacking teams in the league few years ago.
All in all, to me del neri > ranieri any day....