I've used a lot of quill in the past couple of years. It has some tricky bits, but seems similar in a lot of ways to ProseMirror - separate internal representation of data that gets rendered into HTML, delta-based state changes, etc. At this point, I use quill out of momentum - it was the only game in town when I started working with rich text, and now I know how it works. I also like it enough that I've never felt the need to go find something else; it's always done what I want.

I think to fully experience all three of those editors, you should build the following: something that generates a rich text input using the editor, updates a data store (can be just in-memory if you want), and then re-presents the rich text in a read-only format.

With Quill in particular, there's two ways to approach the second part - you could dump the data into another instance of the quill editor, but one flagged as read-only, and let quill handle rendering out all the elements. I don't do that, myself, as it's a bit heavy and relies on the DOM to be present to create the end result (meaning rendering rich text into emails on the server side can be tricky). Instead I use a library (that I wrote) that converts the quill representation into an HTML string that can be later injected into whatever place it needs to go.

In general, I think that's where the one of the important pain points is for any major modern text editor exist - converting the internal data representation into a canonicalized HTML string. This gets further complicated by your framework - it's easy enough to inject an HTML string, and angular 1 lets you even compile that so you can have custom elements there, but angular 2 has no such facility (compiling; you can still inject). So rendering custom elements into angular 2 is feasible but quite tricky.

You'll need to figure out how to handle custom elements too, like at-mentions and so on; those are really domain-specific. How I handle at-mentions in quill (with a pop-up autocomplete) depends on the structure of the overall system as well as the framework I'm in - angular 1, 2 and react all suggest different approaches for this.

Anyway, this is all a long response that means "it depends". Each editor has its own strengths and weaknesses that are exposed by the specific data and presentation needs of your project and the other frameworks in play. But building an atmention or other custom element and converting from the internal data structure to HTML is a good test of functions for all of those.

Prosemirror and Slate both great projects but lack of community interest. They are basically framework for creating WYSIWYG, until they release full featured editor built on it, i dont think it will become popular.

Personally tried both, working with Slate feels much smoother, plugin system easier than prosemirror in my opinion.

And, there is ckeditor5-beta. You might wanna check out.

If you just need a WYSIWYG editor on a web page, and it's a single one, I've used tinyMCE.

On projects where I've had to load up multiple instances, I've had to move away form it as it kept reloading stylesheets and js files for each editor on the page.

Now I usually use quilljs, which works really well for some basic markup.