Cash could do for the short term, 1-3 years, but for me not beyond that. Fiat money does not hold its value well, as Western central banks grow their money base by 5-10% per annum. Non-Western countries inflate even more.
Over a long timeframe, gold wins over cash, as gold reserves grow only about 1.5-2% per annum. By owning physical gold, you theoretically lose that much purchasing power each year, but gain independence from the financial system. It is not a bad idea to keep at least a portion of one's wealth out of banks, brokerage houses and government fiat money. Since 2008 financial︀ crisis, all kinds of perverted stuff has been going on, especially in Europe: Bailouts, zero/negative︁ interest rates, haircut for Cyprus depositors, talk about cashless society etc. If another financial crisis︂ were to happen, ECB could push negative interest rates on to private depositors, start delivering︃ haircuts across the eurozone, or enact other desperate, disastrous measures.
Gold can be bought anonymously︄ by cash, or online by e.g. bitcoin. It can be stored outside one's own jurisdiction,︅ e.g. in Singapore or Switzerland. It does need a safe storage, but doesn't take much︆ space. Seven figures can be stored in a shoebox, although that'll be one damn heavy︇ shoebox.
Silver, platinum and palladium have lower stock-to-flow ratio than gold. In other words, they︈ are not stored in vaults as much as gold, but used more for industrial purposes,︉ which limits their upside. Right now platinum is very cheap vs. gold. If one had︊ a very long investment horizon, one could just keep switching between these two, while maintaining︋ wealth out of the financial system with good privacy.
Long-term, bitcoin has even lower inflation︌ than gold, as the mining reward 'halvens' every four years or so. So, theoretically, it︍ bitcoin wasn't so volatile, it would be even better store of value than gold. My︎ issue with bitcoin is not the technology itself, but the relative lack of privacy-maintaining gateways️ to/from the financial system. If you want to move sizable money in/out of bitcoin, be prepared for a lot of KYC/AML at the exchanges and at your bank. Right now, gold is easier in this regard, at least in Europe.