I have always tried to steer clients to a cms based approach, mostly because it is easier to maintain that separation between content and design. Also it is my belief that the easier it is to change content the more often it might be changed, the web should be a dynamic changing thing, not just a static representation of business plans and marketing speak. Also it helps to protect the image that you craft from their influence 😉
In most of the installs that I have done the CMS serves as the staging server and the ‘real’ site is static rendering of the cms, though there are instances where this is not really the right way to go (I think GSF should be too much of a living site for this to be a plan.) I think it is why I find Markdown, Textile and things like it so compelling, it lets the user think about the writing and lets me control the mark up and the styling.
I would worry though if the site is really image heavy then a cms approach may not work as well without spending a lot of $$, but there are some really compelling opensource CMS’s that a pulling heavily on the AJAX meme to really do some cool things (or at least showing some really potential.
the real advantage to a CMS based site is that it is really Agile and able the change quickly to meet new demands and designs