I like gripper elastic because it makes the shorts stay in place, stops the legs from rolling, grabs leg/knee warmers to make them stay in place, stay flat under tights, etc.

I agree with everyone on the length. Short shorts are for stick figures. Also, longer legs gives more protection when you're on the trail -- either from overgrown poison oak or from unplanned high speed visitations with the dirt.

Pearl and Descente seem to have larger circumference leg grippers than Louis Garneau and Shebeest. I found that TE gave some terrific advice about this when I called a while back.