I think converting altcoins is Bitcoin is better than dollar because dollar price movement is not much in the last some years, where Bitcoin price will definitely provide huge profit soon. Bitcoin price movement is more than dollar. So it's clear, bitcoin is my choice.
Only if bitcoin movement is move in the right direction, imagine if it's drop then an altcoin value will also reduced. However, dollar is dollar, dollar is the Real Currency that accepted arround the world, if you have it you can live where ever you want in the world. He's also the most stable.