The big difference is that you can buy a low-cost S&P 500 fund, and this is a perfectly reasonable thing to have in your retirement account. You will know, ther

The big difference is that you can buy a low-cost S&P 500 fund, and this is a perfectly reasonable thing to have in your retirement account. You will know, therefore, if the SP500 index goes up 1%, your retirement fund has done nearly the same.