Howdy! I’m another one of the developers of React ProseMirror. The way I explained the distinction from TipTap elsewhere is pretty similar to what @tilgovi said here:
At the Times, we’ve been using React and ProseMirror for something close to 5 years now, and have a pretty considerable amount of pure ProseMirror code in our codebase. TipTap is very cool, but it introduces a lot of new concepts layered on top of ProseMirror, so it would have been a very significant project to try to migrate to it.
On the flip side, @nytimes/react-prosemirror tries to avoid introducing new concepts and idioms as a rule. It lets you write React code that looks like React code and ProseMirror code that looks like ProseMirror code, and it handles the seam. We wanted to avoid adding a “third thing” for folks to have to learn; our team already has considerable expertise with ProseMirror, so we wanted to be able to continue to leverage that knowledge.
I expect that TipTap and React ProseMirror are going to appeal to different audiences. TipTap is a fantastic “batteries included” rich text editing library, which is great for teams that are starting something new and are new to rich text editing. React ProseMirror is a small adapter layer for ProseMirror (the way React Redux is a small adapter layer for Redux!), meant for teams that are already comfortable with ProseMirror, and maybe even have existing projects that try to use React and ProseMirror together.