Gold has proven itself to be one of the most durable substances on earth. It doesnt degrade. Every ounce of gold ever mined is still around. (Excluding the small portion sent out of orbit) Gold has proven to be truly precious.
Bitcoins can only be destroyed for a brief moment in their creation during mining under unusual circumstances which likely has not happened. But if the hard drive containing the private key is buried in a landfill, those units are forever gone. You could argue that a pirate treasure chest of gold buried on an island beach and long forgotten is the same end. The bitcoin units exist on the public ledger which is copied into the cloud and thousands of hard drives around the world. We cant predict what may happen to bitcoin in a few hundred years but for todays generation, so far so good. But because bitcoin is officially an experiment, well have to give this one to gold.