For videos I try to turn subtitles off if possible, I find that they do distract me from watching other details on screen. However a lot of times I find myself switching subtitles back on because the dialogue is hard to make out over the background sounds and effects.
Sometimes after watching, say, a TV episode of some show I go online and check the discussion, when I would come across a question somebody asked and I would wonder "Why would they ask that? It was so clearly stated in the show" and then I realized I had subtitles on and was able to read it clearly, whereas another watcher could have missed / misheard those dialogue if he/she didn't turn on subtitles.