I wouldn't call reactivity in Vue "fine grained". Every object that gets loaded into component state becomes reactive, and every piece of code that touches it gets dragged into a massive internal dependency tree.
Vue has blacklisted reactivity, everything becomes reactive (and observed) by default and you can opt-out, while MobX features whitelisted reactivity and is much more fine-grained
Vue has blacklisted reactivity, everything becomes reactive (and observed) by default and you can opt-out, while MobX features whitelisted reactivity and is much more fine-grained