This article examines how different social media platforms affect opinion composition and evolution. We differentiate between product and non-product oriented outlets as they differ in the salience of social cues, thus resulting in distinct user behaviours. We extend prior research in several ways. First, comparing between comments from different types of social media platforms, we show that the product oriented outlets display a tendency to attract polarized opinions. Second, we find that similarity of online comments increases over time, suggesting opinion convergence. Lastly, product oriented outlets facilitate faster assimilation of opinions within the site compared to non-product oriented outlets.