There needs to be a "both" option. I think they are equally important because they play off of one another. When you first see a show, the artwork is what catches your attention and makes you interested to see what it is about. However, the storyline is what keeps you interested and coming back for more. If I had to choose though I would say storyline because, even if the artwork isnt the best, if you are interested in the storyline then you will want to know more about it and will watch it, and remember it.