Is
Star Wars "Science Fantasy"? That's what I've always called it. "Science" for the space ships and "Fantasy" for the utter disregard for physics.
More seriously, I tend to think in terms of types of obstacles, characters, goals, etc. rather than wondering if it's Science Fiction or Fantasy. In the Pern books, there are some references to computers and genetic engineering, but those elements aren't really what the stories are about. And McCaffrey is not a scientist, nor does she claim to be, so the details of the "science" elements of her stories tend to be quite sketchy. Her stories are more about the interactions between people. (Madeline L'Engle was the same way.)
On the other hand, the Lord Darcy books are about figuring things out in a very science fiction kind of way, even though "magic" is used.
I like the term "Speculative Fiction" to cover both, but it's not in common use.
