In 2008, i started a few tests on multiple websites to confirm my suspicion that Wordpress websites are more SEO friendly, or given more weight by Google.

My first test was to convert a static website, already optimized for SEO and used a CSS template to a WP CMS site. This was for an existing SEO client after 6 months of optimization. I changed over the site approx Dec 29, 2008, and I initially forgot to reinstall the analytics code for 4 days after launching the new site (my bad). This actually worked out nicely, as it provides a great landmark for the transition when viewing traffic in Google Analytics. See below. The red line marks the date the new site was relaunched in WP.

envrio-analytics1

Perhaps its coincidence? Only further testing will tell. Please comment if you can attest to your experience with specific software that gives you an SEO advantage.