ahhh. The classic "nurbs or polygons?" question I see every few months. I seriously need to write a universal explaination to copy/paste so I can easily post it again and again to prevent me having to type it all out over and over again.

Polygons:
Easy to manipulate.
Can have their uv's mapped out for texturing.
Have infinite sides.
Surface is made up of vertices, edges and faces.
Are used to create video games. (triangulated polygonal faces only)
Cannot be used as a surface to draw Paint FX on.
Generally easier to use.

Nurbs:
Smoother.
Can change tesselation for smoother rendering.
Cannot map out uv's.
Only have four sides to every nurbs object.
Surfaces are made up of curves. (lofted together you mght say) You modify the curves to manipulate the nurbs surface.
Are not used in PC or video games. (not counting the rendered movies you see)
Are used to patch model. Patch modeling is usually used for very realistic characters.
Can be used as a surface with which to draw Paint FX on.
Boolean operations only avaliable for nurbs on versions 4.5+
Take up less data space.