I think it comes down to usability as opposed to design. I've seen some absolutely beautiful sites (professionally) that nobody could figure out how to navigate, and thus had a low conversion rate. Yet a site that look straight out of a 14-year old's bedroom hosted on Geocities could return more results since the call to action was very clear.
This post talks a lot about this type of usability and speaks to this point (and even mentions A/B testing with usability): http://sixrevisions.com/usabilityaccessibility/10-usability-...