Can anyone elaborate on the advantages and disadvantages of using one type of editor versus the other?
Simple answer, I think, because it works. Which is a lot more than can be said for any in-browser HTML editors I've seen, including TinyMCE. They fall down badly on IE, it has this seemingly unsolvable habit of inserting
<p> markup by itself. I haven't yet seen one editor that knew how to really deal with that, although they all contain hacks to try.
The only reason I know anything about this is because it was such a massive problem at the Microsoft MSDN forums. They accept posts in HTML and render them back in HTML which requires an HTML editor to modify the post. Layout disasters are everywhere. After over 6 years of trying to find a decent editor, having tried about everything from home-grown to 3rd party, they still haven't solved the problem.