My understanding has always been that statis urls fare much better than dynamic ones for two reasons - first, search engines generally prefer them, but second, and I think more importantly, a static url may not stay up long enough to be crawled.

I don't know an extreme amount about the formulas used by various search engines, but i do know Apache makes a tool to rewrite dynamic urls into static ones, so I assume there is an advantage or the tool wouldn't be available.