A lot of my short fiction comes out as science fiction. When I sit down to write something short, I’ve often wondered why a science fiction story pops out. Why do my longer works come out as epic fantasy? I’ve got lots of theories. They’re armchair theories from Brandon the English major, not so much from Brandon the writer.
In science fiction, a lot of times the worldbuilding is easier to get across. Science fiction films have been such a part of our culture for so long, and imagining the what-ifs of the future leaves you with more groundwork to build upon, that in many ways there’s more the reader immediately understands and accepts.
I’ve often said that great stories are about great characters first. But beyond that, science fiction stories are about ideas and fantasy stories are about the setting. I think that’s why when I come up with a great idea story, I write it as science fiction. If I come up with some interesting setting element, like a great magic system, I write it as fantasy. I’ve found that getting across an interesting and complex magic system in a very short amount of time is extraordinarily hard, so it tends to work better for longer stories.