Well, I have never bought real gold so I am guessing here. In stock if you sell the stock and make profits, you will have to pay taxes on your profits. If you don't sell but the stock prices goes higher, you don't pay any taxes until you sell. This is one of the many tricks used by Buffet to lower his taxes.

So since you will be making capital gains by selling gold, I am guessing you owe taxes on that. I am guessing here. Please verify.
If people can buy/sell gold and not pay taxes, then I guess most inverstors would be only dealing gold, why even bother with stocks, bonds and options.