..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.
As much as they can both considered as currency, there are some things you can't purchase with btc. Not because btc doesn't have a good value for it but because the value of the thing needed to be purchased, might just be too low or the merchant prefers fiat. Imagine buying a kilo of chicken from a merchant and wanting to pay an impatient seller with btc. Such situations are quick transactions and fiat is usually a preferred choice.