Plastic. I moved from buckets to Better Bottle and am contemplating a move back to food-grade buckets (with a separate question in the equipment forum). It has been useful/fun to watch the fermentation process, but to get the wort into the BB I transfer it into a bucket and then into a BB anyway, and as others have noted, buckets are easier to clean. If it's easier to clean it's likely to be cleaner. (That said, warm water and an OxyClean clone cleaner work miracles.)
I am a sissy girl and can barely lift an empty glass carboy, so a full one would have to sit wherever I filled it.
One last thing about buckets: less chance of getting light-struck. For my BB fermenters I use an inverted grocery bag with a hole punched in the bottom (after one time when someone left a light on in a closet I use for fermenting), but again, a bucket takes care of that.