There are a number of physical formats you can consider when buying gold:
Physical precious metals like gold are a hedge to the traditional banking system. In a crisis, if the system collapses, it may very well take your property down with it (if it can).
If there is a run on the banks, having your gold under your direct control means they can't confiscate it, block access to it, or have loaned it out in a leveraged fashion.
Having liquid gold on-hand and ready in the event of a crisis is the best hedge. Being invested in gold ETFs is fine depending on your objectives, but if you're truly hedging against unforeseen market collapses, you want physical metal in your possession.
Gold owned through a commodities exchange, or "on paper" is no substitute for physical bars, coins, or jewelry. Exchanges are heavily leveraged, which means if everyone tried to "cash out" at once, there isn't enough physical metal to go around.
Moreover, precious metals are typically meant as a hedge against the complete collapse of the traditional banking infrastructure. If you wind up needing it, you'll want to have it close at hand!
If you're not buying an huge amount of gold, you should aim to maintain direct control over it at your home or other property.
If you're investing heavily, to the point where you need a safe alternative location to store it, be sure to go somewhere like Switzerland with strong property rights. It's key to make sure they can't lend or hedge using your stash.