while this is a bad talk:
The first talk is no-nonsense, no-bullshit, straight focused on the subject matter. It presents most of the api of native browser custom elements by live-coding a little piece of functionality. The second talk is all over the place and contains a lot — far, far too much — of the speaker's personality that nobody really cares about. Plus the language fluency and expressiveness, of course. The second speaker, however, is for whatever reason, popular in the React community, and keeps appearing over and over again.