Oops.. that should have read

.... I am running SolidWorks and I would say w/ great confidence that
" I doubt the modeling ability in Acad "   is better than in SW......

Jarrett [Gotta proof read my proof reads/edits :) ]

Jarrett, The three programs I have manuals on all do parametric modeling
and animation. The differences are in the number and type of sweep rails and
the number of cross sections that can be used to control the shape. The
design tree approach of solidworks and catia both allow reordering of the
design tree and substitution of modified sketch profiles to control lofts
and extruded features in an accessable format. Autocad stores the tree off
screen by line numbers. I only store the last 400 commands but could set it
much higher to store the entir model. It seems to require scrolling back and
forth one line at a time to make changes a cumbersome approach at best. I
just continually make saved copies on the drawing of the elements and solids
and drag them in and out of view as needed.

Solidworks and auticad don't
like to explode a filleted solid to change feature elements once they are
drafted and filleted, although easy access to the design tree in solidworks
allows some changes depending on the mother/daughter relationships as does
catia. The solid editing in catia seems easy to use with drafted and
filleted options both positive and negative with one command on most of the
edits. The pline or spline options on autocad as well as many options to the
mathmatical generation of surfaces and solids in the nurbs modeling and the
ability to use much more complex  sketch profiles is a better fit to my
approach. I tend to research first and then design to specific dimensions
whereas both solidworks and catia use " that looks good to me" type sketches
and rely on dragging the geometry to new shapes.All the systems allow
dragging the  shape definition of sketches due to the parametric
relationships. Also designing using snaps to endpoints and tangents among
others lets the software do a lot of the constraints without actually
declairing them.

All of the high end programs have the ability to assign
surface textures, sheen, color choices, number and location of lights,
contrast of shaddowing etc  to the rendered view and photorealistic
rendering. Solidworks 2010 allows having any background scene  or video
behind the model of a rendered view which I didn't see in the other
products.One thing to look at is how much program you get for the money.
Catia is about 863 MB, solidworks has abour 4.2 GB and autocad is about 5.1
GB, I was using an old version of acad(not parametric but good 3D) and it
was 347MB.

Best I can tell rhino V4 a about 2.4GB but there are a variety
of animal names(flaminco etc) of various sizes and prices. At $2940
solidworks may be the price leader. Then there is the who uses the
software.  Boeing and dassault both used catia for a long time and may still
use it. I am still undecided but need something to design the compound
curves of the airframe parts and patterns and finished parts for the engine.
These parts for the current plane are ready to fabricate but it is time to
upgrade for future projects.

george grimes