I recently found this excellent article by noted marketer Al Ries. He ponders the question of what is more important - the visual or verbal elements of branding. He likens the combination to a hammer and nail and uses BMW as an example of a company that has been very successful by implanting a phrase "the ultimate driving machine" in the minds of consumers. This allows them to leverage visual elements and create a powerful brand image.
Creative Strategy Importance: Visual or Verbal? : Branding Strategy Insider.