Nurbs don't have to have straight lines joining them up therefore you could have more detail for the same amount of control points
This is absolutely correct. 3d Nurbs work on the same principle as 2d splines. The image below shows 2 shapes I created in MS Word...
The lower shape contains just straight lines (like a 3d polygon). The upper shape is made up of spline curves.
Each shape has the same number of control points (5) but as you can see you can clearly get far more detail out of the spline shape, and you can still have sharp edges if required.
