Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.
Ember.js package that provides a classical object model, bindings, observers, computed properties and other conveniences. Great for use on the server or in the browser. Does not have a requirement on DOM.