I haven't tried ProseMirror, but I've can second the endorsement for Quill. For the past three months, I've been working on a large-scale integration of Quill (

I haven't tried ProseMirror, but I've can second the endorsement for Quill. For the past three months, I've been working on a large-scale integration of Quill (with lots of customizations) into a commercial word-processor (https://shaxpir.com https://shaxpir.com) and it has been a lovely experience. A lot of the underlying ideas are similar between Quill and ProseMirror, so I'm curious to hear a knowledgable comparison of the two. But the excellent Quill documentation, as well as the responsiveness of the primary developer to github issues and stackoverflow questions, made it an easy choice for me.