There's a lot of React fans around here, but the two are really not as similar as some may act.
Ember.js is a framework, in every sense of the word. It values convention over configuration, has an idealized tool pipeline(via ember-cli), and a general 'Ember way' philosophy.
React, like Angular, is a collection of parts that don't ever turn into a framework- instead, they're tools to making your own framework. In some ways, this is great- you almost never have the system fighting you because it isn't following the framework's philosophy.
The issue with it, is that understanding a system takes much longer, and often your tools are not drop-in-and-work ready.
Personally, I adore Ember. But I also am a huge fan of convention over configuration, and I enjoy using Rails, which Ember is very, very similar to.
