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.
The Expanse is really good for layperson hard sci-fi. I expect if I knew more about orbital mechanics I might be annoyed, and there are arguably some moments of "stealth in space" that shouldn't work (those are at least quite rare and mostly reasonably explained), but the writing is pretty solid and the story has me genuinely invested.