I think, both of investment are equally much more risky . On bitcoin, we can control full of our bitcoin. The risk, there is no insurance against bitcoin and there is no official central institution that regulates the circulation of bitcoin. If investing in a bank then there is a central bank that governs our money so we do not have the freedom to control our money. Besides that, there are many institution that offer insurance if happen unwanted things to our money. It's a bit of a picture of me so you alone can choose the best for you.