Platinum seems to be absolutely leashed to the price of gold, rhodium has enough industrial users to override any investor spikes.
I agree that the metals market is important to the prepper. I'd look towards a major investment in lead, with minor positions in brass and copper jackets. Ammo can protect what you have, barter for what you don't, and won't feel as bad as handing over an ounce of gold for a loaf of bread.
I don't think one should ever be so cavalier about gold as to equate it to a loaf of bread. An ounce of gold has always been equivalent to a month's manual labor, or the finest suit of clothes the market has to offer. And it always will be that. Its scarcity, reliability and desirability are gold's traditional secret to being the most compact store of liquidity and value known to man.
Yes, gold has its fanatics who make absurd claims, and yes, gold has its detractors who studiously refuse to understand its time-honored traditions. Neither are particularly correct; but to ignore gold is to be left out in the cold at crunch time.