Rodney-
RADEditor has several advantages IF you need them. It also has some drawbacks, well, really only two that I can see.
The drawbacks are 1) You can have custom toolbars per page but not per module instance as of right now. and 2) Older versions of RADEditor didn't have a font color selector where you could choose any color like FCK - editor users could only select the colors the admin had placed in the toolxml file. Apparently this has been fixed on newer releases though I haven't tried it yet. But this could also be a benefit by forcing the end users to pick only theme based colors.
There are numerous advantages though - one of the biggest would be the templates manager since FCK has none at all. The online image editor, image map editor, and documents manager are just a few features RADEditor has that FCK doesn't have at all. Also the Stylebuilder is very cool and makes building some higher end html type content very easy for end uers (i.e. stuff like background images). You can also take a look at this
link for custom tool bars, custom drop downs, custom dialogs, etc. You can enable the user folders ability so that each user has their own folder per manager - and this
link will show you how to enable user folders for some managers and public folders for other managers. (Managers = Image manager, templates manager, flash manager, etc. These are the buttons you click when you want to insert one of the above.)
Maybe you would like to auto re-size all uploads so that end users don't load your server up with a ton of 10mp images? This
link will show you how to do that.
Note - I still use the Telerik built DNN provider for RADEditor instead of the DNN built one. So far it seems that the Telerik one offers more features and flexibility but I would guess that will change in future versions of DNN's RADEditor provider.
Hope this helps.
Greg