Most people buy gold, because they want to diversify and as a safe haven/ for security. Basically keeping their wealth. Bitcoin is a more riskier thing and it is more of an investment.
So they are different. Both have in common, that they are not to easy to buy, but for the average person it will be even harder to get Bitcoin. This could change a bit with the ETF, but you are not holding Bitcoin buying the ETF. But some people also don't buy gold directly, so we will see i guess.