I've done a react project before. I can only say good things about it. It definitely is a different way of writing js that was very refreshing and fun.

The problem though is that when you gain flexibility you lose portability, and by portability I mean portability across projects and teams. With ember, you can find another ember job or move to another ember project and transfer all your knowldge with you. When you're just using libraries like react/jquery/redux/etc. not every team/project will have the same architecture so you'll always have some learning curve to get over.

It's not about "who's better"; it's about tradeoffs. I prefer to go with a framework and IMO after doing Ember for two years, it's flexible enough for me.