When Gold goes up Peter Schiff want you to buy gold miners to increase the gold supply while miners dump gold on the market.

When Bitcoin goes up any miner that comes online increases its value proposition even higher as hashrate goes but supply flow stays constant for 4 years until it decrease even more.

If Gold market cap doubles your individual gold coin may not necessarily double as miners will be dumping more gold on the market. Miners are limited to how efficient they can get on finding gold and gold has no halving every 4 years.

If Bitcoin market cap doubles, your piece of bitcoin is likely to doubles as well as there is a very small constant amount of bitcoin coming into circulation.