If it's something to try and not something I'm vested in I go Dub so I can do other things too. If I'm gonna give it full attention I go sub because the Dub voice actors still can't seem to get the emotion to the dialogue right.
The dubbed is really poor at conveying the emotions of the characters. Also a lot of times what the characters are actually saying is changed to match up with the mouth movements, makes it so you don't really get the full gist of what they are trying to say.
Personally both of them are good with me I prefer reading the Manga especially for Tokyo Ghoul but everyone has a different preference. Dubbed anime give´s the watcher more of that, ¨omg feel because people tend to like to feel in sync with the cartoon¨. Where as sub cartoons are for people who want to know the story.