Original sentence: Fox News currently leads the cable news market, earning higher ratings than its chief competitors CNN and MSNBC combined by average viewership.Measured by unique viewers, however, CNN  achieves 11% higher ratings than Fox News.Most commentators attribute this to Fox's somewhat longer duration "talk" programs interspersed with News updates which cause viewers to tune in for longer periods as compared to CNN's generally shorter news segments
Edited sentence: Fox News currently leads in one of the cable news market's two ratings categories (CNN garners the other).The difference lies in Fox's somewhat longer duration editorial programming -- causing viewers to tune in for longer periods -- and CNN's tendency to include more objective news and less editorial programming