Ask HN: To build a 'very snappy' Rails App - JS MVC or WebSockets?

After seeing this post -http://news.ycombinator.com/item?id=4499845 - by cheshirecat, it dawned on me that I can build a relatively snappy Rails app with WebSockets. I have been wanting to learn a client-side MVC framework (leaning towards Ember.js), but now that I have seen this I am wondering if I am better off just using a WebSockets Ruby gem. I know this might not be the 'typical' HN question...but if I ask this question on any of the forums for the client-side MVCs, I am likely to get a skewed response (obviously). I asked on Stack Overflow - http://stackoverflow.com/questions/12359978/to-build-a-very-snappy-rails-app-js-mvc-or-websockets - but because this is more of a 'discussion/debatable' question, the mods thought it wasn't a good fit. So I am hoping that some HNers that have experience with this stuff can shed some light on which might be a better approach for me....along with the pros & cons for each. Thanks.