Fiat currencies could never be considered store of value because their value is decreasing. If someone will hide a big amount of fiat under the ground to make sure he has something to spend after a decade or so, he will most probably have so little to buy with that same amount by the time he digs it up. The problem with fiat is that it is not valuable in itself unlike gold or even Bitcoin to a certain extent. Fiat is just a piece of paper without value.
Gold is just a metal, and BTC is just a cryptocurrency whose value is currently calculated in USD. Nothing in the world spontaneously gains value, we are the ones who value it. In terms of value store, the better side of BTC than USD is that it is limited, as a updated money. Otherwise, a method of payment that is self valued in the world and fully meets the value of each valuable asset has not yet been discovered. Actually, when we think we are the ones who value everything, I do not know how we will be able to get such a payment method.
I don't know if we can consider gold as just a metal. There is no other metal that shines like gold. Metals are quite common, we use them to build houses, create coins, make spoons and knives and forks, and so on but they are the most common metals. Easily accessed thus cheap. Gold is not like them. It is very limited and does not rust and shines really bright. And this is perhaps the beginning of the value of gold. It is just different. And it will always be valuable in the years to come.