I think deciding on this will be hard and frankly subjective. My suggestion is that you try both for a small project and decide for yourself what makes you feel at home. It should not take more than a couple of days to assess it yourself.

As for me, I decided to go with Ember.js. To be frank the final decision was between Ember and Angular (over all other frameworks) and I felt that getting past the learning curve of Ember, it made me comfortable. Most importantly both are close/past the 1.0 release.

If you do choose Ember, I would recommend the following:

- Watch the peepcode's emberjs cast https://peepcode.com/products/emberjs (and code it up)

- Go through the Emberjs documentation on the site, though very likely you will not know how to build a big app. It is still necessary to hone your fundamentals.

- The 1.0 RC1 that was released yesterday has dependency injection, if that matters to you. My opinion is to just code as little as possible and prefer to stick with the framework's conventions (i.e not use DI).

- Use a sound build tool. I don't have Ruby/RoR background and so preferred to use Brunch.io (http://brunch.io/) - Nodejs pipline. They have a Emberjs skeleton available to get started quickly - https://github.com/icholy/ember-brunch. I believe there is a rake pipeline tool for Ruby/RoR folks as well.

- Ryan Florence recently released a scaffolding/build tool Emberjs - https://github.com/rpflorence/ember-tools. I use this to develop my skeletons and use it with my Brunch.IO setup. It is a good place to start and get past the learning curve. The tool will probably become the go to place for building Emberjs apps sometime later.

I am sure you will find similar tools for Angular.js but I think you just have to try something simple in both and find out for yourself what makes you comfortable with these opinionated frameworks :).