It's not quite that simple Polly. The question could be framed as: is 6 or so years of Kelly better than however many years we get from Cerra? Could be one or two and a trade, could be 12. Kelly is a very good player, but I'm not sure if he's going to be twice as good as Cerra.
Kelly is a great story, and anyone who saw him in the state game against the Vics would have loved to have seen in purple, but before you throw rocks at the club, I'm not sure anyone here would have taken him with a top 5 pick. Not having a second round pick meant he would have needed to make it through to the third round. He didn't.