Over the long history of its existence, gold has gained a reputation as a stable asset, this is a good way to invest since the movement of its prices will be gradual and smooth without jumps and falls. You can make money on investments in gold, but this will take a very long time, since the gold rate is growing very slowly.
That's the flow for gold, it's increase isn't volatile as bitcoin so it's slow.
Bitcoin allows you to earn very quickly due to the volatility of the same rate. But there is no certainty that the price of the coin will only grow, the value of BTC may collapse and deprive its investors of all income.
Only if you're strong hands and you can surpass the days of bearish times. There are times that bitcoin won't be good after the time you've bought it because the price varies. It can be lower than the price you've bought and that can lead to panic for some newbies.