I don't think you can make a conclusion about FX vs. Physical Commodities as far as risk and return when it comes short term trading. During different periods you will find that one asset class in more volatile then the other. During Brexit, for example, (although extreme circumstances) the FX market was accompanied with high swings. On the other hand, you will find that during news announcements from API, USDA, etc the physical commodities may be accompanied with higher volatility.