Fantasy. Just because bookstores put sci-fi and fantasy together under "Fiction" does not mean they're the same thing. Sci-fi is an exploration of what could happen in the future when advancements in knowledge have changed our setting and capabilities, and how people would deal with the changes. Fantasy is an exploration of what could happen if the existing physical laws of the universe were different and how people would deal with those conditions.
The Star Wars setting is the only successful example of combining sci-fi and fantasy that I can think of, and it has exactly 1 fantastic element (the Force). And that only worked because Lucas set the entire setting "Long long ago, in a galaxy far, far away" which created the necessary distance for acceptance.
So that's the line for me. Get your fantasy in my sci-fi or vice versa, and I'll throw it in the rubbish and order again.
The Star Wars setting is the only successful example of combining sci-fi and fantasy that I can think of, and it has exactly 1 fantastic element (the Force). And that only worked because Lucas set the entire setting "Long long ago, in a galaxy far, far away" which created the necessary distance for acceptance.
So that's the line for me. Get your fantasy in my sci-fi or vice versa, and I'll throw it in the rubbish and order again.