It gets a bit awkward there because the interest return is afaik taxed as it is earned through income taxes while the gold return is capital and taxed at sale.

I know in Australia if you are looking for wealth preservation it is a hands-down win for gold but I don't know enough about the US tax system to comment on what would happen. I suspect the returns are a lot less rosy and it turns out most of the real wealth ends up being transferred to the government.