I think it has elements of all three. Noir, slasher and commentary, although the commentary is more pronounced in the sequel. There is some deliberate symbolism in how Sarah is more cold and calculated in the sequel because of her determination for her mission and is typically lit in a cold blue light in her more determined scenes, while Arnold gradually becomes more human in his demeanor and through the run of the movie is eventually more often lit in a warm light. Of course, a lot of people think the sequel is pretentious... But I'm not one of those people.