This was the case in Angular 1 - in Angular2, not so much. The component-tree structure (much like React) allows far smarter optimization on change detection - both with immutable data structures and observables - entire subtrees of components can be removed from the change detection step until the state notifies it of a change.

Good reading material by a team member - http://victorsavkin.com/post/110170125256/change-detection-i... and http://victorsavkin.com/post/114168430846/two-phases-of-angu...

An early beta comparo - http://www.roblog.io/js-repaint-perfs/angular2/opt.html vs http://www.roblog.io/js-repaint-perfs/react/opt.html - should probably update these with the latest RC.