Fiat for daily use.
While bitcoin or cryptocurrency for investment.
It's the embraced use of cryptocurrency today but we have to spend it in the most possible way to enjoy it. I have used it to shop for many times but our society is not yet ready to go all-in with crypto.
It is like choosing whether pulling off your wallet to get some money or pulling out your phone cause you have something to scan and pay. Although I'm a huge fan of crypto, I would still choose the fiat since it is the one that we are using now and the complexity of using the crypto is not yet settled, there are still bugs and errors to be fixed. We are on the process of transitioning, sooner or later we'll be having it.