IMHO, AutoCAD for
Mac is a very undeveloped program that is still in the very early stages, and if you've primarily used AutoCAD on a
Mac, you're missing out. I have no doubt that it will be developed further into something far more useful, but at present, it's not nearly as easy to use as the PC version.
That said, I am experienced with both programs, and I use both all the time. AutoCAD is really useful for schematic diagrams and
working drawings, either where you need higher specificity, or where you aren't really working in scale (such as for signal flow diagrams and such).
Vectorworks will always be my first choice for light plots. It seems that
Vectorworks is much better suited for designer drawings, where you don't necessarily have a specific dimension in mind - it's very easy for you to draw a shape and then fudge the size until it fits into the world in the way that you want it to. AutoCAD seems to be much better when you already have specific dimensions, such as when turning a designer's drawings into TD drawings.