Everything depends on what you mean by SHTF. Different events are going to result in very different situations. Do you mean:

1. Total infrastructure collapse: Whether by EMP, solar flare, or some other national disaster. In this case, crypto will be worthless, but so will anything that isn't immediately useful. That includes gold and silver. The only things of value will be food, land, and the means to defend them. During this, which is essentially total anarchy, no one will be trading valuable goods for a chunk of rock that he can't immediately eat or shoot. Precious metals won't have any value until some civil order is restored.

2. Civil war: Since the infrastructure to support them will still exist, both precious metals and crypto are likely to retain their current value, though crypto will be much easier to trade for small goods. However, all involved factions will likely be printing their own currency, so you're probably much better off just using your faction's currency, and fighting like hell for that faction to win.

3. Weimar-style hyperinflation: Again, the infrastructure will still be around, only the fiat currency will be worthless. Gold, silver and crypto will still hold value, but as N0rds points out, stores are not set up to manage transactions with gold or silver, especially if you're dealing with values like 1/1000 oz. It's far easier to process 1/1000 of a bitcoin; and most stores are already set up to manage such payments.

To sum up: Gold and silver are better stores of value, but don't count on them having any liquidity. Crypto is much more liquid, and easier to process, but also less stable and more vulnerable to market fluctuation.

And you arent paying for mountain dew with gold or silver, either... Not a single store accepts gold or silver, but thousands of them DO take crypto...