Its more of a personal preference than anything. One of the reasons people prefer subs over dubs is that subs preserve the original dialogue better, which is lost if the subs are dubtitles anyway. Dubbing has a particularly bad reputation in anime circles due to the butchering by companies like Harmony Gold and 4kids in their heyday, which makes anime watchers leery of anything that isn't brought over as is too. There is nothing wrong with glossing over puns that wouldn't work in English or modifying cultural references in a manner that they work in the west, but altering the dialog into something it never was (see: Mewtwo Strikes Back) or calling rice balls donuts is unacceptable. The timings of the dubtitles match with the dub too, and not the original audio, so it can often make for a subpar viewing experience.