My mom's an architect so I just nabbed her version of AutoCad and have been learning that. It's a good program because it's used in so many forms. You can download the symbols for all the fixtures (they're on google, type "stage lighting cad symbols") and they can easily be opened and used in the program
I wouldnt recomend autoCad as one it doesnt work on mac, Two its a $900 or so program. So stick to vector works it has a steep learning curve but once you know it your set in the industry.