Of the several differences between USD and Bitcoin, which one would you choose now? because in general both are also very much needed.
As many people know that any traditional currency has special characteristics which Bitcoin does not have because Bitcoin is not supported by any authority.

Features of traditional currency:

• Divisible — can be converted into smaller pieces for specific uses such as paying a certain amount or micropayment.
• Non-consumable — cannot be consumed for purposes other than the exchange of value.
• Portable — can be easily carried around.
• Durable — doesn't wear out or depreciate over time or under certain conditions.
• Secure — cannot be faked.
• Easy to transfer.
• Rare — cannot be replicated indefinitely.
• Fungible — each part has the same value as its equivalent.
• Recognizable — recognized and accepted as a means of transaction.

As for Bitcoin as a whole, unlike traditional currencies:

• Has no central authority claiming it supports money.
• Is subject to deflation due to artificial scarcity, while central banks can print more money at any time.
• Whether every transaction is forever recorded on an immutable public ledger.
• Requires transaction fees to be paid to miners.
• Transactions are carried out over the internet and include a public address.

Source:

• https://twitter.com/BitcoinMagEDU/status/1572950463883919361/photo/1
• https://cryptonews.com/guides/difference-of-bitcoin-from-traditional-currencies.htm