What are the major differences (pros/cons) between ember-model, ember-restless, and emu?

Of the three, I have only used ember-model (and of course ember-data).However, I did evaluate the other two, ember-restless, and emu as well.

I picked ember-model because of the following reasons:

• Created and maintained by Erik Bryn, who is also a core EmberJs team member
  • This is important to me because I have a view to switch to ember-data when it is ready, and ember-model appears to be most aligned, both in syntax and style, to ember-data
• BYO$A (bring your own AJAX) - ember-model is not prescriptive at all about where resources should be.
  • No need to worry about URL path conventions, and needing to override them
  • Allows me to construct my own XMLHttpRequest, and do whatever processing necessary before loading the records
  • (ember-restless and emu behave mostly like ember-model' RESTAdapter, and do not give this degree of flexibility)

Although I have not personally used emu, I would say that its unqiue feature is that it has built in support for push updates to models. While this is a rather nifty feature to have, it was not a requirement for me, and I chose ember-model.

While this is not quite the in-depth comparison that you asked for, it was enough for me to make a choice, HTH.