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.
I believe that fiat money and cryptocurrencies are not the same thing. You say that BTC is money, then according to money BTC should be used to pay for goods and services all over the world, but this is not. I would call BTC a new asset for saving and earning. As for money, there will probably be new digital money in the future, and each state will have its own. You must understand that no state will ever allow anyone to create their own money, and there is logic in this. Therefore, cryptocurrencies are probably some kind of experiment with an as yet unknown purpose and task. But no matter how it was, cryptocurrencies have already made their contribution to our lives and it will probably continue.