Feature-wise, Next does seem like a superset of Gatsby, especially since it can support server, static and hybrid rendering models. Architecturally, Gatsby does have some advantages. They're not ones that are particularly important to me, but I don't think it's fair to ignore them:

- The plugin model is more sophisticated, and there's a huge ecosystem of them which can solve most common use cases.

- The ability to use a unified data graph means page invalidation and rebuilds upon data changes can be done automatically at a very granular level -- because it's possible to keep track of which pages would be affected by every piece of data.

I'd add that I have issues with both, which leads me more to Next.js because it has a lower level of vendor lock-in compared to Gatsby. Anecdotally, migrating a small site from Gatsby to Next.js replaced 150 Gatsby-related imports with 10 Next.js ones.