How is superhuman better than Gmail?

It's not. They largely use the same keyboard shortcuts and you lose some foldering/organization functionality.

At first, you won't see why it's worth the bother to learn SuperHuman. Once you learn it, you will not want to go back. In short, it's faster and easier to organize your mail (the "splits" feature). Automated snippets give you canned responses to common questions. (I reply to marketing offers from Gmail addresses with a canned response to an affiliate link to write better emails.) I wrote a detailed report on my experience with SuperHuman here, and I've been using it for about 18 months so far. https://primarygoals.com/why-use-the-superhuman-email-client/