I disagree that only a limited amount of gold exists and that that's why it is protected from inflation. Who knows how many places which are still unexplored could contain gold. Cash is out of the question in that regard. So Bitcoin is the best like you said. 
Cash can buy anything, no limit at all, while bitcoins have. the disadvantage of bitcoins was if there is no connection, how can you access your wallet? unlike if it is already converted into cash, you can. when it comes to Gold. Gold prices also fluctuates, its price was depends on the exchange rate of dollars. Gold can be use to pawn or sell at higher price. I still want to invest on bitcoins than gold.
I agree, the cash right now mm single use anywhere. A Bitcoin - this alternative currency. Everyone chooses himself than it is convenient to use