Goldman Sachs is the latest to weigh into the gold vs. Bitcoin (BTC-USD) debate after JPMorgan argued that the rise of cryptocurrencies in mainstream finance is coming at the expense of bullion."Gold's recent underperformance versus real rates and the dollar has left some investors concerned that Bitcoin is replacing gold as the inflation hedge of choice," the bank said in a research note. While there has been some substitution, "we do not see Bitcoin’s rising popularity as an existential threat to gold's status as the currency of last resort."Institutions and wealthy investors avoid cryptocurrencies due to "transparency issues, while speculative retail investment causes Bitcoin to act as an excessively risky asset. We do not see evidence that Bitcoin's rally is cannibalizing gold's bull market and believe the two can coexist."Bitcoin has had a wild month, challenging $24,000 yesterday after passing the $20,000 milestone for the first time on Wednesday. Gold's