Twitter Followers are more likely to induce advocacy and future purchases than Facebook Fans who often become fans or "like" a brand on Facebook because they already use your product or service and already a fan in real life and according to eMarketer.com, it may be more difficult for them to actually increase their spending or advocate for the brand more than they did before “liking.”
Daily Twitter users who followed a brand were more than twice as likely as daily Facebook users who “liked” a brand to say they were more likely to purchase from the brand after becoming a social media follower. What’s more, Facebook fans were the most likely group to actively disagree with the question. Subscribers to opt-in marketing emails fell in the middle.
Marketers looking to push out the most effective messages to opt-in recipients must understand how audiences differ across channels and what causes them to connect with brands. Marketing venues that seem similar may differ strongly if their users have different needs and motivations.