It really depends on what you want.
Studying literature is a great way to improve your writing. You'll familiarize yourself with classic (an not-so-classic, depending on the class) forms, internalize language and the rhythms of language, etc. You'll learn about themes and see lots of different ways of communicating those themes. I commend you for seeing that these are all very valuable lessons.
But a creative writing class will have a more direct application on your writing specifically. You'll get feedback on your writing from your professor and possibly your fellow students. How comfortable are you with sharing your work and hearing criticism of it? If you are not good at taking criticism, then all the creative writing classes in the world won't help you.
The other consideration is the professors. What do other students say about them and about the classes (especially the writing class--in a writing class, the prof has much more effect on the tone and usefulness of the class than in any other subject)?
I have a master's degree in publishing & writing, and most students (English undergrad majors were exempt) were required to take at least two lit classes. I chose the most unusual ones, and I loved them--American Indian literature and Science Fiction literature. A traditional lit class would have been less helpful to me. But my writing classes (workshops, really), also provided specific insights into what I was working on at the time and went a long way toward helping me focus on my novel.
So--lit classes are great for general writing ability, while writing classes are good for the specifics of your writing. Which are you more interested in working on right now?
And maybe you can take the one you don't pick in another semester.