Question: What is the difference between using the WYSIWYG module pointing to the CKEditor library and using the dedicated CKEditor module.

We currently use the WYSIWYG module with TinyMCE.

Answer: 
Using the WYSIWYG module will allow you to fairly easily switch to another editor if you find one you prefer (or if new ones come onto the market).
RE: WYSIWYG module using CKEditor library vs CKEditor module

I found the former only allowed the following toolbar;

[![](https://i.stack.imgur.com/GOrzE.png)](https://i.stack.imgur.com/GOrzE.png)  

(source: [johnathanthwaites.info](http://johnathanthwaites.info/sites/default/files/toolbar.png)) 

Later had much more like font colour, flash embed, spell check etc.

[![](https://i.stack.imgur.com/lABox.png)](https://i.stack.imgur.com/lABox.png)  

(source: [johnathanthwaites.info](http://johnathanthwaites.info/sites/default/files/toolbar2.png)) 

Have done a full explanation here;

Link to [CKeditor](https://web.archive.org/web/20170509000520/http://johnathanthwaites.info:80/Ckeditor)