According to a recent Pew Research Center study that analyzed Nielsen data relative to the 25 news websites with the largest number of unique monthly visitors, Facebook is a more valuable source of traffic than Twitter.
Most traffic to the major news websites was directed from Google (30 percent, on average), The Drudge Report and Yahoo, but outside of that realm, Facebook fared well and proved to be an influential medium for driving news traffic. For example, 8% of the unique monthly visitors to The Huffington Post and 6% of those to The New York Times come through Facebook referrals. On the contrary, the Los Angeles Times is the news website with the highest percent of traffic coming from Twitter, yet Twitter referrals only account for 3.5% of its traffic.
Another interesting finding from the study, which was highlighted by Mashable, is that 35 to 40% of the traffic to the news websites came from links on other sites, rather than through users directly typing in the website's URL or clicking from another page on the same site.
All in all, the study provides some interesting points to ponder, especially among those who are constantly struggling to stay on top of the most influential mediums for spreading a client's message.