If I had to choose, I prefer fantasy in novels, and sci-fi in films.
I love it when I get an unexpected crossover, though... I just finally got around to reading all of Terry Brooks' "Shannara" titles; I'd read the earlier ones when I was a kid, but hadn't checked out the later series. The second book of the "Voyage" series takes a weird sci-fi turn; totally caught me by surprise! One moment, it's all "swords 'n' sorcery"; the next, he's talking about giant AI systems utilizing magic-weilding elves as energy sources?!? It was cool, though!