I agree his defense is his biggest flaw IMO, he needs to improve that end of their floor before he becomes one of the elite PG's in the NBA. As for PG's, I agree it's the deepest position in the NBA currently with PF as a close second.
I don't know about PF, a whole bunch of bad apples spoil that bunch, plus, not a lot of them are two-way players. Same thing could be said for SFs.
I can honestly say that SG to a point is the deeper position in terms of two-way players, or people who are -REALLY- good at one side of the ball. Examples being players like Tony Allen, Shumpert, Kevin Martin, etc. Then you have some underrated two-way players like Nick Young, Wes Matthews, Captain Jax, healthy Richard Hamilton.
But the thing is, there is a huge gap between some of these players, and the rest that fill out the league. SG is really top-heavy I think in terms of people I would be willing to play 33+ minutes a game, and it just gets sad after the 15th shooting guard, while in the PF position, I'm comfortable with playing most PFs in the league good minutes, only getting scared when I get to a guy like Drew Gooden or Charlie Vill.