Designers all have their own preferences when it comes to CAD programs. I try to stay in a wide triangle of CAD and visualization suites, with my favorites being Vectorworks 2008, WYSIWYG (I have R21), and AutoCAD. It seems that every few years I encounter a reason to brush up on one of the three, so I just got proficient on all three. Go figure.
AutoCAD users can benefit from a new build of a lighting-specific design and CAD program called LD Assistant, by Design and Drafting. Christian Choi, a standard in the concert production realm, wrote a fantastic review of the product for LiveDesign Magazine. Check it out.