Well it will all depends on your intended use for the item. As a water storage etc garbage bags will be better but as an emergency sleeping bag/shelter I would rather have a space blanket around me. I find space bag to be used for one purpouse only and that is shelter. I will still carry both because of durability issue. Space bag is not rip proof enough to substitute a real garbage bag. I can take a black garbage bag and use it to make a poncho, bed liner, water heater, emergency sled or temp roof. It would be a waste of money to do the same with a space bag. Yet using a space bag for keeping you warm after plunge in the river is no match for a garbage bag.