答案

For the purpose of having more fun, I would definitely choose an art class rather than a science class. For one thing, taking an art class is usually quite enjoyable, especially when you learn painting; you can use various colors and shapes to satisfy your fantasies. For another thing, many art classes such as sculpture require the use of your hands instead of your mind, which is very relaxing. On the contrary, science class always requires students to do advanced research or calculation which needs lots of efforts. Most importantly, unlike science classes, students who take art lessons have very few assignments and almost no exams. That would put less pressure on the students and enable them to have more fun.