iirc the standard jewel case is polystyrene. it gets more brittle with age. I never throw out a jewel case when I trash a computer disc and when I buy used CDs I can replace the frequent broken lids from the spares. They break way too easily, imho for example, if the opening force is not in exactly the plane it needs to be in.
The super jewel case is made of thicker material. It has a much better hinge. Some are polystyrene too , others are better materials, but even if it is, it is a better design and should be much more durable. They are on sale for various prices on fleabay mostly more than I would care to pay for an empty case. Poly styrene ones start at about $1.00 each and go up to prices where there ought to be a disc of good music included.
The cardboard digipaks do seem to occupy less volume ( a serious advantage) but the surface of the disc (whichever flavor of disc) is pressed against the cardboard. That can't be good. The center snap support of a jewel case would seem to me to be advantageous. I think the digipaks are trying to make an unconscious connection to LPs. they should have a microfiber inner sleeve.