umm... nurbs dont step up in actual detail when your doing that. Its just shifting through resoultions for display, so working in one will yield the same results as working in three.

You should use NURBS in a very light way. try and achive a form in as few isoparms as possible. If its getting rediculously complicated then maybe rebuild your surface so its simpler, no matter how dense or light the control surface is the rendered surface can be of an infinite resolution.