I have mentioned before that there is no "best" Content Mangement System out there. People often ask me why I use so many different ones among my varied blogs. I use many to be familar with many. I even briefly played around with a bare bones straight php CMS.
Seth over at Enter Content Here has penned a good article on what to think about and what not to think about when choosing a CMS.
I agree with the concept of thinking of the CMS in terms of how and not what. Your objective in choosing a CMS should not be "I want something to manage my content perfectly"… It should be something more along the lines of your companies mission statement or such.