Honestly I believe bitcoin is better since one you don't use your credit card so you don't loose you needed cash but instead your cash that you could easily earn back from mining. Plus, it's open to all ages unlike credit cards.
My answer Is we need both because bitcoin ate we use to investment and to use a payment. But we need too our own currency to buy are needs too. They are both big help in our daily lives. We need to consider to some people that don't have ability to use bitcoin yeah i know bitcoin is better but we need too our regular currency.