At the company I work for we recently did a massive migration from Backbone to Ember. The reasoning behind this was simple: prior to the funding round we had recently received that led to an influx of new developers, we had one senior FE guy who was customizing and building this all himself. It became a decision of convention the senior's way vs convention in the standard means of how it is defined in a framework. This is why Ember was so attractive: it is both powerful and maintains a rails-like standard on how you build an application up and out. On a personal project, I would totally use Angular or Backbone, but when maintainability is a question the convention of Ember is a clear winner in my eyes.