[tech2000]

You probably could just go with the stationary mount as long as it keeps the projector safely out of reach of people in the cafeteria. You could probably save yourself some money by going with the stationary mount too, unless money isn't a problem.
If you do get the motorized projector mount, you just have to remember that if you are dropping down 20-30' (do they make motorized mounts that long?) that you will always have to stop it at the same place to get the projector image to sit on the screen. Also, you are running cable(s) to the projector too, which could create problems with the motorized part of the mount. I haven't really played around with these motorized mounts so I am not sure how the cabling would be run.