I don't know enough about your taste in movies to know which one "should be" voted for. But I think it's a pretty fair question: one movie represents the ultimate in intellectual science fiction with an art-film, sometimes narrative-lite dynamic that breaks the classical formula, while the other is a narrative film with strong emotional pull, little ambiguity, but strong core ideas and presentation. Although I certainly think one is better than the other, I can see why people would prefer Close Encounters over Kubrick's masterpiece.