I like both, but I've always leaned toward science fiction myself. I have an easier time finding deep and thought-provoking stories in the science fiction genre, and I tend to prefer its more emphasis on exploring what its possibilities mean and using them to examine ourselves.
yeah having a reason is good. being cool, or novel, or an interesting metaphor for something are all good reasons. like brainbeam says, uncritical support for the eternal capitalism hell engine film