Rondo is the smartest, but is sometimes too smart for his own good. Some of the things he sees ahead of time not even Deron or Paul can see. But then again, sometimes he sees tries to make things happen that aren't there. An enigma, but the most curious/weird combination of talent the league has seen maybe ever. That triple double he got last season was just plain stupid. Nearly 20 in all three categories.
Chris Paul dominates the ball a little too much for my liking, but he's a hell of a player. PGs who are that involved in the offense from a ballhandling perspective don't win championships, historically.
Deron Williams has an amazing handle, and is an all round package. Hasn't played on a decent teams for a couple of years so its hard to tell where he's at, but I like the way he can mix his assists with early initiation of the offense. He should have a great year this coming season.
Then a step down from them you have Rose and then Westbrook, who are just plain athletic freaks, but I wonder how long their bodies will hold up playing that helter skelet brand of ball. Also they are both more combo guards than PGs.
If I had a contender, I would rather Williams or Rondo; if I had a struggling team that I needed a PG to put on his back, take on opposing sides all by himself and will a subpar roster the playoffs, I'd take Paul.