For now it is more dominant cash because ATM or bank is everywhere. But if later bitcoin already exist bank and its ATM, maybe people just open handphone and scan barcode to do transaction hahaha 
In the future, bitcoin doesn't even need atm anymore because all can be controlled via smartphone, bitcoin atm in my country didn't get a good response because android makes everything easy, cash money for the future is virtual, not currently so popular because the world economic system still prioritize fiat, many offline shopping also not using bitcoin.
Bitcoin value changes every day cash value not change. It will use full one in the future. If save the bitcoin it is use full for the future growth. We can not judge Cash is changing in the future. But bitcoin value change any time. Bitcoin price is increasing day by day. If use bitcoin you will know it. You will get easy to get profit.