So my advice is to pick an interesting project which you can build using modern techniques like ember or react. That way you have greater motivation to learn and you get results for the work you have done.
Ask "What should I learn _next_, ember or react?" instead.
(My opinion is that you should _always_ be learning new things that interest you. Learn them both - what you're _really_ doing is learning how to learn better. And _that's_ the skill you _really_ want. Unless you're just looking for resumé keyword fodder, in which case just grep your local job ads, I'd bet Angular would rank higher than either ember or react right now - at least where I come from.)