Static by rule of thumb is always the better way to go. dynamic will still do fairly well in the search engines as long as you follow certain rules with it.
1)Static links to the content. This means if your going to link to it keep that link in the same place. Random link of the moments don't go over very well with spiders.
2) never use &ID= Google has publicly stated that it ignores those pages.
3) Keep the general content static. By this I mean let the template change dynamically. Let the menu's and links change dynamically, but let the content remain intact and in full on each dynamic page. Even putting a little constantly changing words in the middle of the text will make the whole page disapear. I learned this one the hard way.
4)Create a sitemap on a static html page. You can update it with cgi, php, asp...whatever. Just keep the sitemap 100% static and uniform.
5) create an obvious flow to the site. I ran into this problem once because I used a detailed search using pull down menus and check boxes(which was the obvious reason why my site was 100% dynamic). I solved this problem by creating links to the path each option would take you at the bottom of the search. Ie.
First option.
I hope this helps a little :)
Eli
Fully dynamic content and SEO - going from static to dynamic
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