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.
We need both. We definitely need both. At least for now.
We can't buy day to day household commodities like the groceries ... etc using Bitcoin. Most vendors would only accept fiat, at the moment. Maybe this may change and we can use Bitcoin for everything. This is the same for internet shopping. Sites like Amazon and eBay remain in their adamant stance against Bitcoin. They only accept PayPal, but not Bitcoin. This is quite strange as bitcoin has much more qualities when compared to PayPal.
In the future, this may all change. Bitcoin may become adopted by many merchants after they understand the benefits of using it. Until then we need both Bitcoin and fiat to survive. Well ... we can survive with only fiat but not with Bitcoin. So if you want to use Bitcoin, today, then you also need to use fiat. There is no other way.