Performances: <button onclick=(action 'someAction')> VS <button {{action 'someAction'}}>

In this amazing video (PhoneGap Applications with Ember: Lessons Learned | PhoneGap Day US 2016 - YouTube) Alex Blom talks about “hacks” in Ember for mobile world.

At 22:00 he says something about <button onclick=()> vs simply {{action}}.

Can you say something more about this? What he really means? Is today still like this?

It works just for <button> tag? And for <a>?