I do block both. Mainly, I am interested in blocking all the noise that I have no interest in viewing on a page. Apart from ads, that includes certain banners and bars and it definitely helps. Anything I don't need I don't want to see and so no point in loading and displaying them, and that largely includes comments. I almost never venture into the comment sections, save for a few that I am presently whitelisting. This exempts a site from all the content rules, though, which is why I look forward to partial whitelisting. I also block adult sites for no real reason. 😎