I'd rather hold both of them, I know there's a lot of benefits of holding bitcoin instead of cash for ex. if you have cash or money in the bank it will take time to gain interest but if you are holding bitcoin for sure you will earn something or lose just little amount. The reason why I also want to hold cash its because in our country not all merchant accepts crypto/BTC and if there are emergencies or needs I can use my cash in hand.
You do not need to exchange 100% your capital to cryptocurrency, but to be honest, I think you should put 60% for cryptocurrency if you only want to use crypto and FIAT. However, if you want to saving in gold and real estate or just simply use for your business, 30-40% is enough for your investment.