Which would you invest in?
BTC is much more volatile than gold, so let's say the choice is between $1k in BTC and $10k in gold. Or maybe the gold investment is $1k in a gold miners ETF which leverages the price of gold. You get the idea.
BTC and gold fill the same theoretical niche in a portfolio, which is to say, a "store of value" hedge against currency debasement and socio-political/economic turmoil.
BTC has one significant advantage over gold, which is portability. You can carry millions of USD with you on a flash drive. However, BTC has two major disadvantages which make it unsuitable as a full portfolio stand-in for gold:
1. Gold is "the original asset class", and has been around since time immemorial. It is a 100% tangible asset whose properties are well understood, and for which there are many centuries of data available to evaluate its portfolio performance under a variety of political regimes and economic scenarios. BTC is a novel asset class with no such extended history, whose performance and properties are not very well understood.
2. BTC is subject to a variety of specific risks and vulnerabilities which gold is not. Its portability also makes it insanely vulnerable to loss or theft (both physical and digital). Its value relies on the proper functioning and operation of other complex systems: electricity, the Internet, the BTC network and crypto exchanges. One or more of these are likely not to be around when you need it most. Finally, within the crypto space BTC is subject to enormous "competition" from other coins and has numerous well-known technical disadvantages, such as the extreme inefficiency of its network. At any time, the BTC market could be killed off by a combo of government repression and the emergence of alternative coins which are much more secure, efficient, and usable, institutionally-backed etc. and thus far more appealing to both serious investors, and non-techie everyday users.
For all these reasons, an "investment" in BTC is really a speculation - thus it should make up only a tiny fraction of your investment portfolio. This is actually a huge problem for BTC in the near term (next 5-10 years). It's been two years since the bubble peak and the market is well below the highs reached at that time. Yet, market sentiment remains dominated by HODL'er hard-core true believers who claim to be "investors" waiting patiently for the Big Move, but are in reality classic bag-holding suckers who will mostly puke out on the next move lower.