Knockout JS

• Nice tutorials and documentation.
• Nice to have in the smaller project, especially when you are satisfied with something which just provides UI data bindings.
• Difficult to unit test.
• Code separations is a concern.
• If routing is required, then we need to include a new library for it.

Angular JS

• All-in-one package. Provides everything you expect from a MVC framework.
• Built and maintained by Google.
• Extends HTML and at the same time pollutes DOM!!!
• Quick development.
• Easier to unit test. It provides a unit testing API.
• Steep learning curve.
• Very little boilerplate.
• Fewer tutorials and not very good documentation.
• Becoming very popular with dev community.

Backbone JS

• Nicely documented and very stable.
• Relatively old and extensively used.
• Lightweight and small. Therefore widely used on phone also.
• Incomplete framework.
• A lot of boilerplate.
• Clean separation of concerns.
• Strong force to follow certain pattern. Results less reusable code.
• Misses on UI bindings.

Ember JS

• Relatively new.
• Need a better documentation.
• Unique support for composed views which increases code reusability.
• Provides everything which angularjs does.
• Uses Handlebarsjs for tempting views.

Things not covered and assumptions made in the assessment:

• Performance: It is a very subjective matter and depend a lots on the bottlenecks of your application and on the criteria you use to judge it. Backbone is quite extensively used in mobiles and tablets so shouldn’t be a problem at all. Both Ember and Angular claim that they give snappy performance on phone though there is no use case to support this, at least I didn’t find any.
• Sources: Its a mix of my experiences with these frameworks and information gathered from various resources which I consider reliable.