If you are certain that you want motion, I'd go with one that takes standard screw in floodlights. The quartz lamps are very bright but get very hot and tend to burn the sockets. Plus you have to search for replacement lamps.
If the light is for security, I'd go with a dusk/dawn 13 watt compact fluorescent fixture. Long life lamps and about 25 cents a month to operate dusk/dawn.