What do you mean with 'they take the same swings in value'?
I agree that when comparing bitcoin as an investment to sdice as an investment, no need to convert in USD. Is that what you mean?
I think so.
If you have some US dollars and are considering investing in Apple stock, you don't take the price of oil into account (unless you're also considering investing in oil).
In the same way if you have Bitcoin and are considering investing in SDICE, you don't take the price of US dollars into account (unless you're also considering investing in fiat).