Nurbs are nice because they have a very clean typoligy, so even if your modelling a head which would be harder to rig up nicely in NURBS you can convert to polys/ sub div and get a very nice typoligy if your using 1:1 span nurbs patches.

Basically for a beginner a good rule of thumb is that polys are good for practically everything, but for some objects such as space ships or extremeley curvey forms it may be wiser to use NURBS due to the fact that you can achive a nie curvey surface with very little geometry. e.g. a boad.

But it boils down to what your modelling and what you prefer to model with. As Saiyan said, try both and see which you perfer.