I prefer PGs that can get their teams to advance in the playoffs. Rondo and Westbrook did the best job this past year doing that.
CP3 had a rather pedestrian playoffs, barely getting his team by the Griz, and then getting swept by the Spurs. 17/5/8 are decent numbers, but the 42/33% shooting was middling and he barely got to the line, 1.7 FTs attempted a game.
There's no doubt what NBA PG elevates his game in the playoffs. Rondo scores at a 50% higher rate, rebounds at a 40% higher rate, and assists at a 15% higher clip in the post season. Rondo's 17 points, 6.7 rebounds, and 12 assists in 2012 are great playoff numbers, almost catching Magic's career playoff marks of 19.5/7.7/12.3
In terms of passing Rondo had one of the more dominant (compared to the rest of the league) postseasons ever. He had the 7 highest games for assists in the playoffs and 9 of the top 10. He had just over half of all the games with 10 or more assists. He had just over 4 more assists/game than anyone else in the league, the 4th highest margin ever.
TP.. And what are PG's supposed to do again? Oh thats right.. DISTRIBUTE
I'm actually going to say a point guard's role is to orchestrate the offense.
Since most teams are different, most point guards are expected to do different things. You look at a guy like D.Rose, where their entire offense is rolling around his ability to attack the basket and dish out, and you see he's going to have to score.
CP3 is basically the coach of the Clippers--I'm sure Vinny doesn't call plays--and you can see it when he's moving players around, shouting at people, and only puts up his shot when its the best option.
Westbrook's another one... the Thunder need him to hit those pull up jumpers, because if he doesn't all they've got to do is pay attention to Durant. Any team can beat Kevin Durant, but not many teams can beat Durant and Westbrook both going off at the same time.
Deron Williams's job... is to loaf around the last two seasons because his teams sucks and he's a Debbie Downer, then show up for some hilarious yet-inconsequential-event like dropping 57 on the Bobcats or shutting down Linsanity.
Point being, Rondo's the best player for the Celtic's offense, and all the other Superstar PG's tend to be the right guys for their own team's.