We use both; local component state as long as nobody else (might) be interested (this usually the case for generic components that are not application specific, such as page controls, checkboxes etc). But as soon as state starts to creep upward in the component tree, we move it directly to global state and store it in observable data structures (using mobservable) so that any component interested can use the data in whatever way it was delivered (through props, global state, closures, etc) and (un)subscribe automatically.
