For example with an Euro based PP and an US based PP, they could be AIMed vs one another.
From what I've seen across historic Japan, UK and US 1972 to 2009, the PP provides similar returns no matter which one you opt for. You'll generally get around what you would have done from investing in a domestic PP than what you get from investing in a foreign PP. The currency changes sort of balances it all out.
Depending upon which one you invest in however will see different components moving by different amounts.
Consider the 2008 crisis period. Generally UK Gilts (BGOA) didn't do as good a job as US TLT at countering stock declines
However the pound declined relative to the USD, so from a UK perspective Gold rose more in price than it did in the US and overall compensated for around +20% compared to the -20% difference between UK Gilts and US TLT.
If you run a form of arbitrage metric against a UK PP versus US PP when rebased to the same currency then the two do overall tend to move somewhat in lock-step (but some potential arbitrage opportunities periodically become apparent).
So there may be some benefit to running an AIM like rebalance between the two. The downside to that however is additional costs and potential tax liabilities.
In the UK gold is capital gains tax exempt if held in Sovereigns. Gilts are CGT free, pay gross income and if held in an ISA gross=net. Cash can be invested in a 1 to 5 year Gilt ladder and also be effectively tax free. Yearly capital gains tax allowances of around $15,000 can be used to rebalance stock in a tax efficient manner. If however I employ a US PP then I become liable for much higher costs (withholding tax etc.).
A gross=net type investment return is comparable to quite a larger taxable investment return i.e. 9% p.a. tax efficient PP might = 12% p.a. taxable PP.
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