personally I use mylar, have yet to check out the new diamond mylar though, but if not high gloss paint is the next best thing, with the added advantage that if you have a nute spillage, need to wipe down due to pests, or general cleaning then paint is better.
Plus there area no nooks and crannies in painted walls, whereas with mylar pests can hibernate in corners or even on the back side of the mylar against the wall.