Ember.js: Which one of angular.js and ember.js is the better choice?

I've found both good, and used both. Depending on what do you need it for.
For example, I found Ember better for biggest applications, with many models. But Angular beautiful to work with, due to the fact that you need to write a lot less code.

But both are good frameworks, just choose the one you think will fit your project better.

I've done some experiments with both (though not real world experience), I found Ember.js to be often excessively sophisticated, it's the kind of frameworks that takes all decisions for you. It's very complete (and heavy, though for a JS Mvc app I think is not terrible) it comes with much more out-of-the box, but IMHO I think is bloated with complexity, and unnecessary levels of abstractions.

Angular.js seems more natural and straightforward to me. The approach to most problems is very simple, and that's a big cumpliment. eg. Angular doesn't try to abstract html (as Ember), but embrace it.
the way databinding is solved in angular is brilliant and simple, and it has just the necessary abstractions to structure your app, a module system with support for dependency injection.