Ease of access to and exchange with global marketplaces. I can transfer/trade directly from/to El Salvador without any bank being involved in that transaction.
A bank by any other name is still a bank. Sure there is definitely a legal difference such as deposit insurance and access to their lender of last resort. For the customer however it doesn't matter they still need KYC, the cops can still see their transactions, they still have to ask where the money is from, they can still knock on your door and put your hands in handcuffs. Many of the advantages to people in El Salvador with BTC is avoiding extreme inflation in the national currency. However one does well to note that inflation woes in the Atlantic world actually correlated with a partial deflation of the Bitcoin bubble, so if you're in the EU/US bitcoin is an investment when money is cheap, not a hedge for your money becoming cheap.
If you need to keep your money on an exchange to be able to do transactions, you'll probably still need to go through a bank or exchange or the same thing by any other name.