To everybody trying to make this into a tech fight about Angular vs. React/whatever, I've been repeating this like a mantra and even mentioned it in a talk on javascript once[0]: You can argue about the minor details of the tech stack till you turn green and blue, but Angular wins because it succeeds in the only metric that really counts. jQuery: (for reference) 5,656 commits 7 branches 122 releases 199 contributors…
The number of committers only gives you some insight to any three of these things, and can actually mislead you. The Javascript ecosystem is ridiculously fast moving (which is a nice way to put it :)) so number of committers doesn't tell me if all those folks will just jump onto the next thing that comes along. Also, the Javascript community has developers of a wide variety of skill levels, so the number of committers doesn't necessarily say much about the quality of the library without understanding who these committers are. I'd argue there is often a small number of key contributors to any open source project, with other folks contributing small patches to fix bugs or minor enhancements, so the total number of committers doesn't tell you a much more important thing: who are the key contributors, what is their background and views on software engineering, and how likely are they to remain committed to the project over the long term?
It seems to me the main thing Angular has going for it is that Google has bought in to it, so that means no matter how flawed it is (or not), it's not going anywhere anytime soon so you can be sure security fixes and bugs will continue be addressed over the long term. Then again, Facebook seems all-in on React (and I'm not sure about Ember) so maybe this isn't much of a differentiator.