Reach vs. engagement — which one actually matters?

A post reached 50,000 people and got only 10 likes. Another reached 5,000 and got 500 reactions. Which one actually succeeded?

Reach tells you how many people saw a post. Engagement tells you how many cared enough to act — a like, a comment, a share. Engagement is usually the sharper indicator of content quality.

Reach tells you how many saw it. Engagement tells you how many actually cared.