I'd consider things to be a subjective question. Almost like asking whats better, blue or red? You're bound to get a variety of answer based on what a particular person likes most. Ok, that said are are some pros and cons for each.
Polygons (boxmodeling): if you're designing for games the decision is pretty much made for you as this is what you'll have to use. In sufficiently high numbers, polys can be made to look smooth (contrary to popular perception of polys). Most people tend to start their learning with polys as it seems to be easiest to grasp conceptually and it is bit like sculpting.
Nurbs: once the domain of character/organic modeling since they are curve or spline based, are still used heavily on any models that require very smooth curvature. However, since they are built up of patches, they can be difficult (though not impossible) to animate. Certain aspects of Nurbs modeling will appeal to engineers and carpenters. Revolve is a lathing operation. Lofting is a hull operation similar to ship building. One cool thing with nurbs is that you can specify the output geometry of surface creation functions (i.e. you can tell a revolve function to end up with a polygon mesh vice a nurbs surface).
Subdiv: Sort of the best of both worlds, working with subdivs in polygon proxy mode is very much like working with regular polygons except that the results are much smoother like Nurbs. Subdiv modeling tends to be very processor intensive though. Unlike Nurbs, subdivs create a single shell which is generallly easier to animate.
The latest versions of Maya make it very simple to convert from one form to another, so you may find yourself using the different modeling methods for different types of objects only to convert the mesh to a different type later. Avoid excessive conversions, if you can, as it tends to make "heavy" meshes.
Again, a very subjective question.
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Last edited by mhcannon; 11-02-2005 at 03:26 PM.