I think the biggest difference is that Nango lets you customize & extend the unified APIs on the platform.

Usually unified APIs mitigate their limited catalog with passthrough/proxy requests. But this is a partial solution, since you go back to having a lot of integration logic in your code base.

With Nango these customizations live in the unified API itself and benefit from all the infrastructure available there (OAuth, rate-limit handling, pagination, de-duplication of records, etc.). You can also build entirely custom integrations in Nango.

That being said, I think open-source unified APIs have a ton of promise! It is great to see the ecosystem grow :)