You're right. They're both speculative in nature. I'd argue against gold as an investment for that reason. Think I'm crazy? Get educated.

Compare gold to the DJIA since 1900.

http://www.macrotrends.net/1333/historical-gold-prices-100-y...

http://www.macrotrends.net/1319/dow-jones-100-year-historica...

And don't go comparing Bitcoin to gold in any event. It doesn't have the history behind it, and there are too many instances of investment fads that die hard.

Incidentally, the value that grew, and that you would have extracted in dividends, is not reflected in the share price. Also, the DJIA is weighted by the share price rather than the market capitalization of each component. (Really, it is that absurd as an index!)

Anyway I agree with your point that while the economy has surged over the past 116 years, gold has been tradeable for an ever-decreasing share of economic output or share of the available real assets, and has been far outpaced by how a conservative portfolio of equities would have performed over the same period.

While a distinction can be drawn between real economy and money or financial economy, currencies, like the US dollar, are defined as legal tender by the governments that are backed up by significant real economies.

Official currencies can be devalued relative to real economic production, either intentionally or through mismanagement, but they are not an act of faith like betting on precious metals that have long since been deprecated as official currency.