I would say with Angular, what you write is not javascript , it is Angular JavaScript, which gets compiled into javascript on running over compiler. Having been worked with GWT for many years, I am disappointed with Angular doing the same mistakes of not allowing the developers to think in terms of Javascript. But in terms of the framework, which they had brought in.
However, Backbone gives me lot of freedom in customizing the app by adding Javascript and using its model view observable logic. If i find any shortcoming in backbone, i can see a plugin available in the Community. Which is really great.
To conclude , If your are experienced JS developer (JS ninja), you will love backbone. If you are intermediate/beginner JS developer you will love angular. However, this is just my perspective.