Often modelers like to identify a single, master surface as the main component of the model. Converted geometry primitives are good if you want the starter surface to become the master surface. See . Point and CV surfaces are good as starters for rectangular surfaces.
Going immediately to the Modify panel avoids the problem of creating additional top-level NURBS objects, which you can't use to build relational, dependent sub-objects. (The exception is using curves for loft and sweep surfaces. See , , , or .)
Two general references for modeling with NURBS are Curves and Surfaces for Computer-Aided Geometric Design: A Practical Guide by Gerald Farin (Academic Press, fourth edition 1996) and Interactive Curves and Surfaces: A Multimedia Tutorial on Computer Aided Graphic Design by Alyn Rockwood and Peter Chambers (Morgan Kaufman Publishers, 1996).