The biggest win of crypto versus fiat is that crypto is global, fiat is local.
You have dollars, sterling, euro and MANY more fiats that you have in your country and it is really difficult to take it
outside of your country, has a lot of fees. With crypto you need not any forex exchange and you can carry it instantly around the world anywhere you want without any fee and you can send it to anyone around the world without any additional fee.
Indeed, anyone can now start trading without any permission needed. Trading and in general having a bank is a luxury that a smart % of population can afford. Bitcoin is a real gamechanger that can bank 4 billion people, and by then 1 coin will be worth millions of inflation-adjusted dollars.
Cryptos and fiats have their own dominance or superiorities.
In terms of usability, it's obviously fiat's since they have more usability from around the globe, like USD for example. I'm pretty this currency is used at almost all parts of the world, if not, all countries have exchangers that accepts usd.
In terms of transaction speed, it's crypto's since it's almost instant when transferring money with them and it doesn't have that much of a fee (only around 2cents more or less).