BIG difference.
If you are talking about the paper LDs than you are correct.
But if you're talking about the metal coins then whoever accepts them can just sell the coins for the value of the underlying metal in the coin.
The 'whoever accepts them' is contingent on someone knowing the value of the underlying metal is equal to the face value. And just who would that be? Do you really believe the usual business owner will be knowledgeable enough to allow the acceptance of such coinage by his employees? Would you accept such coinage on the 'promise' that the underlying value is equal to the face value?
And what if you're convinced, and accept the coins? Will your bank then be equally accommodating when you try to deposit them in your account? Or will the next businessman be so accommodating when you attempt to use them in buying a lb. of beef?
No. Gift cards have value because they've been purchased with legal tender. Liberty Dollars only have value if the person who's asked to accept them finds them of value. Look, if you want to run out right now and stock up on these, more power to you. And I'll wish you luck. You'll need it.