I just read a thread on another site I belong to that fell along these very lines and I wanted to open it up here.
The gist of the argument was which would do the most for SEO. The pro-on page optimization side (mostly SEMers) were indignant that anyone could think that page content was not the most important factor to SEO. The more SEO oriented people admitted the importance of the on-page optimization was important it was not as important to overall SEO than back links/anchor text.
Reading it the break seems to be, understandably, that the SEM people are thinking in terms of user experience and the SEO people are thinking in terms of page rank.
Let the debate begin.