The padding of the fully filled ski bag can completely wrap the entire cargo space. This kind of ski bag provides you with maximum protection in addition to a hard protective cover.
Partially padded ski bags provide some protection for your gear. This filler may only be in the tip and tail area, which is the key point where you don't want to damage the gear.
An unfilled ski bag cannot provide much protection from improper handling. This type of bag is most suitable for business trips, light travel or storage.
Ski bags without padding are sometimes called board sleeves. Like non-padded ski bags, they do not provide much protection.