Our experience has shown a much higher hit factor to FB as opposed to website when both are presented during marketing. I believe this is do to familiarity (seems everyone has a FB) and trustworthiness (they trust it since they also have a FB account)....so it has marketing value.
Facebook and social media in general are a vital part of a marketing strategy today. The larger your "social footprint" the more credibility you create for your company and your website. Google is a lot like your human friends, family and customers; the more it sees your name around town, the more likely it is to trust, recommend and remember you. Facebook is the big player right now, but also don't forget Google+. Quality content that is also linked to G+ will consistently out-rank content that is not on G+.