Technically Sci-Fi and fantasy are the same.
If it's got magic or demons, it's fantasy.
Harry Potter is fantasy.
Science fiction is based on imagined technology. Star Trek is science fiction.
Sure, both may have invisibility cloaks, for example, but Harry's will involve magic while in Star Trek it will be based on alien technology.
Think of Joss Whedon, for example. He does both.
Serenity is science fiction whereas
Buffy the Vampire Slayer is fantasy. My favorite author Lois McMaster Bujold has three fantasy novels out, but she's written nearly a dozen science fiction ones. The rules are different. Things can happen in a fantasy novel that can't happen in science fiction. Sure Harry Potter and Dr. Bashir might both ride a broom, but Bashir's better have some sort of anti-gravity flux-capasitor attached or I'm not buying it!
Carol