I read a very interesting article on testing the database speed and efficiency of WordPress Premium Themes by web development company foliovision titled What’s wrong with paid WordPress Themes: WooThemes vs ElegantThemes where foliovision says:
There’s a lot of talk about how professional paid themes are in comparison to free themes. It’s not what we’ve found. Cutline, Twenty Ten and Oulipo are all much better coded than any theme we’ve found at WooThemes or EleganThemes.com.
As I own a number of Premium WordPress Themes and Frameworks, I decided to do some basic speed testing for myself using foliovision’s recommended plugin WPDB Profiling.