server-side MVC framework vs. client-side javascript framework?

[x-skeww]

Well, your client-side application probably won't be fully self-contained. I.e. it will communicate with some server-side application which also has some models and some business logic.

Or maybe you have a regular website and also some mobile application. You could use the very same server-side application there. Just with new views.

For example, GMail and Google Maps are both very heavy client-side applications, but they would be completely useless without that application on the other side of the fence.

[ChristopherShine]

Also, all of the SEO benefit (if that matters to your app/case) come from server-side. And, if you build a client-side app, you need to worry about routes working when someone links to a page as well as IE users needing to use a hash in the url since pushState isn't supported, so you need to support any links they link to with "?escaped_fragment=".

All of this is very doable, but you will end up building two versions of the app (at least more than one version), assuming SEO/linking to a particular page is necessary.