Fiat and cryptocurrency are the same but people in society differentiate them and value fiat because its adopted by the government far back, and since the existence of the world and also a specific country, so from my research I find out that government just disliked cryptocurrency for nothing,
So differentiating fiat from bitcoin is valueless because irrespective the importance and massive adoption of fiat currency from its existence before cryptocurrency, it's obvious that fiat is money and bitcoin is money, their functions and contribution in society never depart from each other, so bitcoin now is the shortest way of transactions across the world without much process or procedures, using bitcoin everything buyable is easier to purchase without stress, so from my perspective I prefer bitcoin than fiat currency due to fast transactions process across another country, and nothing fiat can purchase bitcoin can't purchase, so no difference between both because all are currency.
Only thing they have in common is that they both currencies
fiat is controlled by central banks crypto is controlled decentralised from community
fiat gets inflated and depreciates because of inflation while crypto has limited supply and price goes up the more people use it
governments disliked crypto currencies because they cannot control it from their central banks but its obvious is the only way forward for currency
and thats why they will also start to adapt and to adopt it.
soon there will be no fiat because crypto will replace fiat