Thanks for pointing this out. I’m going to quote a twitter thread made by @luisherranz not long ago, where he explained our main differences with Gatsby.
1. Frontity is 100% focused on WordPress.
This means the number of concepts to learn are minimal, it doesn’t need any complex configuration to get you started and the APIs that WordPress developers use to create themes are tailored for the things they usually need.
2. It’s rendered dynamically.
This means people don’t have to rebuild the HTML each time they modify or publish something. Our preferred approach is SPR (https://zeit.co/blog/serverless-pre-rendering…) although there are many ways to configure it. It’s as fast as a static site, see the example: https://mars.frontity.org
3. It’s opinionated
It has its own state manager and CSS solution. Thanks to that people don’t need to learn things like Redux and at the same time it powers a very flexible extensibility pattern, more similar to the one of WordPress itself than to the rest of JS frameworks.
We have a section inside our documentation covering this matter, but I agree that it would be a good idea to improve it comparing different use cases and features.