I did a similar evaluation a couple of years ago and ended up with TinyMCE. One of the reasons is that TinyMCE treats <Return>-key as a new p-element. The team (or the man) behind TinyMCE seems have the "right" attitude regarding web-standards in general. It is also important that TinyMCE supports Opera after Opera added support for content-editable in version 9 or something. Though in Opera the <Return>-key generates br-elements. I have the understanding that this will be fixed in the future by Opera. The Safari support is probably limited.