Everyone in this thread brings up great points. Only thing I would add is if you are just now learning React start with the tutorial on their site and when you are searching for answers to problems and see people using ES6, ignore it. Just focus on what React is doing and understanding how React actually works.
Learning the fundamentals of React is very important and requires 100% of your attention. If you try and learn both at once this will probably slow you down from learning React and also introduces things like Babel and Webpack. Take it one step at a time. Learn React.
Thats my two cents.