But the physical realm is not immune to scam. Suppose you have 100 gram coins, someone could start "chipping" them so they each lose 1 gr, after chipping 100 coins you get 1 "free" coin right? actually you just stole that from others. Sometimes they add back the lost gram but using a cheaper metal, and sometimes the practice was done by the State. Indeed in the Roman empire it was done that way
This cannot be done in the digital world, not with something as secure as bitcoin, where every little satoshi is accounted for. With physical coins you would have to carefully check each coin, this is unscalable and unpractical. If if you get a "certificate", you its different than trusting a bank "to keep it stored...". You trust whoever certified it, and besides the physical good could always be tampered with after certification.
Therefore Bitcoin is more secure than gold.
in the sense of counterfeiting, yes. there are other considerations, however. for example, if quantum computers were to break ECDSA tomorrow, it would irreparably harm bitcoin. gold is not vulnerable to such cryptographic vulnerabilities nor power grid/internet failures. in those senses, gold is more secure.
in the end, bitcoin may have superior monetary properties and potential utility, but i believe both will stand side by side as store-of-value assets in the future.
technical sidenote. dont worry about quantum
it will never break ecdsa by tomorrow. it will just reduce brute forcing to be from millions of years to thousands of years.