We have two sites, one that is set up through WordPress and one through Drupal. Although the Drupal site is older by about six months and has a lot more content etc, the speed and SEO by far out performs that of the WordPress site. Take what you already have and fine tune the site. There are modules for Drupal to help with SEO, it just takes some research and time. The added plus is that working with Drupal (although it will take a bit longer to learn and implement) will make you and your employees more well-rounded!
