I personally think Jabari is way overrated. I think he is one of the best offensive players in college but after watching him I don't think his game will translate well in the NBA. I think his weaknesses is:
1)Very poor defense and I only expect it to get worse in the NBA. He is undersized to guard big forwards and too slow to cover Small forwards. Did not see any improvement throughout the season on defense and was benched many times during the season due to his poor defense. It doesn't do much good to score 20+ points a game if your giving up 20+ points per game. It will also make Favors less effective on the defense side of the ball because he will have to help out a lot and teams will be able to break down our defense.
2) Very poor shot selection even though he can score and is a good offensive threat in college I think his poor shot selection combined with being undersized he will struggle in the post. If he plays SF position the players guarding him will be just about as tall but much quicker and Jabari won't be able to get his shot off as easy.
3)I think he will have to play power forward in the NBA because he is way to slow to guard quick Small Forwards meaning he will take time away from Favors or Kanter. I do think he can be effective as a stretch four and score some point from the outside when he has bigger guys on him, however he will give up a lot on the other side being a poor defensive player and undersized on the inside.
For these reasons I think he would be crazy to stay another year in college, he should take the money while its there. If I was drafting I have him fourth behind Wiggins, Embiid, and Exum. I would not be surprised if he declares for the draft to see his stock slip a little from now till draft day. This is just my opinion and I know many here are high on him, we will just have to wait to see how things turn out.