It is not more popular but what's sure is it's safer, better and pricier. Invest in bitcoin when you still can before Bitcoin take the leading role 
!
!The supply of bitcoin is also much smaller than usd, As far as im aware usd can have practically an unlimited amount so is valued somewhat differently to bitcoin.
Agreed. Bitcoin is smaller but popular in terms of safety and not to forget heavy transactions. USD transaction would cost you surcharges and taxes to be paid on document. However you can save little of that if you transfer money in terms of bitcoins. People do not need any identification or chaotic documentation process to get such transaction done. So bitcoin or USD both have more or less same popularity, it's just about personal choice I believe. :-)