C3PX said:

I would call anime a "style" more than a medium.

I would say that all styles are a kind of medium. Styles and techniques are simply means that we use to achieve different results and, as such, can be analyzed in terms of their suitability for a given subject matter. For instance, a lot of anime (like DBZ) uses very large eyes as a way to artistically emphasize the types of expressions people can make with their eyes. The more complex the eyes are drawn (DBZ eyes are generally simple), the more beautiful this technique of emphasizing facial emotion can be. That's a medium if you ask me.