Bitcoin is always better than cash.For our bitcoin earnings,we are not accountable to government and we need not have to pay taxes unless it is legalized in the particular country.With bitcoin,we could easily send huge amounts of money with very low fee at high speed.With bitcoin,our money value increases,but with cash,our money just remains idle.
Remember that the government of a certain state/country runs because of it's people taxes. It's an advantage for personal reasons not to pay taxes, but it is a selfish act to do so.
To answer the question, bitcoin is NOT better than cash...YET. The mere idea that bitcoin is only useful because it has a "cash value". And not everywhere and not every time you can use bitcoin or any other cryptocurr to purchase goods or pay for services. Possibly in the future, digital currency will be the next big thing.