(Biased Quill author here)
Most modern rich text editors have or are moving towards having a document model that maps to the DOM, ideally also producing compact and canonical output. Quill's new document model Parchment takes this approach as well though I admit I borrowed the idea from the Etherpad guys, and some design ideas from React as well [1]. I have not had the time to dig into Draft.js in depth but Facebook has made many high quality contributions to open source and looking forward to borrowing more ideas.