Ember vs MarionetteJs

Ember already defines the general application structure and organization for you. This was done to prevent developers from making mistakes which would needlessly over-complicate their application. While it's still possible to go out of these practices forced to developers by the Ember authors, you still have to go out of your way to force them.

Ember-CLI is a very useful tool. With just a couple of commands it scaffolds the code, installs dependencies and finally compiles everything itself. It's very useful to quickstart an Ember project.

Ember's preferred templating language is Handlebars. This is mainly because Handlebars is a logic-less templating language and Ember tries to keep it's logic outside the view.

Another reason why Ember benefits from Handlebars is mostly aesthetic as Handlebar's clean syntax makes for easier to read and understand templates.

Finally, Handlebars templates are compiled instead of interpreted, which means that they are much faster to load.

Ember follows the philosophy of "convention over configuration" meaning that it already has almost everything configured for you, so you just have to start coding and developing your project right away.

Ember is practically a complete full-stack front-end framework. It comes with it's own asset pipeline, router, services etc...

The Ember Guides are well structured and very well written. The API documentation is also fantastic.

Most of Ember's components come from the Ember Object Model. It's the basis for views, controllers, models and even the framework itself. This means that the framework is extremely consistent since almost every component shares the same core functionalities and properties since they are all derived from the same object.

Route handlers for the URLs can see a wide range of possible application states, asynchronous logic in the router makes sure of Promises. And implementing makes sense.

It batches bindings and DOM updates to increase performance; if similar tasks are added to a batch, the browser would only need to process them in one single go, as compared to re-computing for each task one at a time.

Ember's API are really easy to understand and work with. It has methods which allow you to harness complicated functionalities in an easy to understand way.

Ember's new router need much less boilerplate code that it previously did.

Ember also has a debugging tool called Ember Inspector which is used for debugging the client side of your app.

You can use any of jQuery’s features.

EmberJS provides with an extremely handy feature of advanced bindings. With this you can not only set the path to the binding value in your app but also set in which direction you want the changes to propagate to (oneway, single, multiple etc).

Promises represent an eventual state in asynchronous logic. Having promises everywhere (almost) means you could write simple and modular code, using almost any API that Ember provides.

Having custom properties in your templates is itself a huge plus but having custom computed properties is an even greater benefit, since now you can code your custom function as a property and call it from your template. Hence rendering your page exactly according to your needs.

Ember comes with built-in routing capabilities. There's no need to install third-party plugins to be able to use routes.

If you've used handlebars (Ember.js's templating is powered by HandleBars) helper tags in your code (like {{#each}}) you won't have to worry about updating your template each time you add/remove data from your page, Handlebars will auto update your template for you.

Not in my experience but maybe the project I am working on was poorly put together

The project I am working on has memory leak issues although I think that is coming from Knockout