Sproutcore is an advanced HTML5 application framework.
I have seen a lot of post where they are claiming that ember.js is much better than sproutcore but looking at the differences i have seen that the widget support is not there in ember.js
When to use SproutCore and When Ember
From the technical standpoint ember.js is focused on more modularized code and so called semantic-templates for views;sproutcore is more monolithic
Differences between Sproutcore and Ember