Statistically, more people have got rich using USD than BTC.
If you want to increase your chances of getting rich, use USD.
Maybe there should be a thread listing people who have become rich from bitcoin. I bet the list is not very long.
Do you mean using "USD" like going to job every day,earning just regular salary in USD,is that what you think about?
or i just got it wrong,and you mean about investing into USD and other currency? because if you are talking about the second thing,
i think that bitcoin is better to trade with small bankroll,because of the big moves we see on it's chart.