Although they all generally have the same duty (run the offense!), different point guards in the NBA possess a variety of skills. Whether they are big or small, quick or fast, or aggressive or passive, they come in all shapes and sizes...Is the ability to shoot three-pointers well a key skill for point guards?The short answer is yes.
I would guess that better shooter = more efficient offense holds true across all positions. I suspect the next step is to study whether the difference of affect for point guards is appreciably different than that for players at other positions.