Please note that i am referring to the free version of Sketchup. The commercial version may be more sophisticated. Here are just a few examples.Originally Posted by Dave Richards
1. The dimensioning tool in Sketchup is a very crude manual operation. Autocad has a world of dimensioning options to make life quick and easy.
2. The tools for drawing arcs, circles, curves and ellipses are very limited. Autocad allows you to draw these elements in a wide variety of ways in relation to other elements in the drawing. This is hard to explain unless you have experience with programs that suport these functions. The bottom line is, Sketchup forces you to draw all sorts of temporary construction lines and points to achieve accurate placement of these elements.
3. The tools for replicating objects in a drawing are much more powerful and sophisticated in Autocad.
4. Autocad can export and print drawings in a wide variety of formats and scales. For example, the .dxf file format is an almost unversal format for exchanging information between design programs. I would guess that the pro version of Sketchup will also do this.
Having said all that, I would have to agree with Mark D. that this program is quickly becoming the standard design tool for the woodworking community. It can be learned with only a few hours of practice, whereas becoming really proficient in Autocad (which I am not) takes days of training and months of experience. That is a huge benefit to people who are more interested in woodworking than drawings. I think it is agreat tool and am amazed that Google is giving it away!