There are a number of physical formats you can consider when buying platinum:
Platinum 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!
Having liquid platinum on-hand and ready in the event of a crisis is the best hedge. Being invested in platinum ETFs is fine depending on your objectives, but if you're truly hedging against unforeseen market collapses, you want physical metal in your possession.
Physical precious metals like platinum 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 platinum under your direct control means they can't confiscate it, block access to it, or have loaned it out in a leveraged fashion.
When investing in any asset, including platinum, it's important to keep the time horizon in mind. Prices fluctuate, and over a longer time horizon there's a better chance of your investment appreciating in value.
The last thing anyone would want is to invest money they'll need in the coming months, only to have the market move against them. Talk to your financial adviser, and carefully plan any future purchases.