Strength to support your top while rolling on the jack and in long-term storage. The perfect balance means there is no danger of your top sliding off. It is safer for the user, as it does not require you to climb up to your ceiling to install it.
The RollnJack allows you to park right under it and save on space: a valuable feature alone. Ceiling hoists/ winches can also end up being very costly if they drop your top or damage your garage ceiling, not to mention if you get hurt installing them.