Super Pony
Studded Muffin
A lot of stories or settings can flip from one side to the other within the space of a paragraph. It's the razor's edge between "science!" as explanation and "mysteriousness!" as a foundation.
A zero g knife fight will hit my brain as science fiction, but a knife fight where the combatants are wishing themselves through open space with happy thoughts (Star Wars here)? That comes off as fantasy. A super intelligent post-human creating a wormhole nexus on earth is fairly science fiction...that same dude using his magic to fight off chaos sorcerers and his turn-cloak clone of son (WH40k here)? Well that's fantasy. A ship's crew trying to invert a reaction process to vent a certain type of particle stream at an on-rushing astronomical event? Science fiction. That same crew being teleported from one end of space to the other by a magical trickster (Star Trek)? Well that's pretty fantastical.
Fundamentally I think all science fiction HAS to have a bit of fantasy in it...otherwise it'd just be fiction, using current known science to support a story about man vs self, man vs man, man vs ...etc. However, the degree that various offerings of science fiction seem more SCIENCE fiction or science FICTION depends on the individual reading/playing/viewing. Mary Shelly's Frankenstein was science fiction. Does it still hold up as such? Should we now put it into occult fantasy, or horror fiction instead? Is Walking Dead science fiction or science fantasy? What about Battlestar Galactica? To me there are elements of classic fantasy in all of these...as well as some "science" that lumps them into the sci-fi family.
TLDR; To me Science Fiction is the genre, Science Fantasy is the opinion of the reader/viewer/player.
A zero g knife fight will hit my brain as science fiction, but a knife fight where the combatants are wishing themselves through open space with happy thoughts (Star Wars here)? That comes off as fantasy. A super intelligent post-human creating a wormhole nexus on earth is fairly science fiction...that same dude using his magic to fight off chaos sorcerers and his turn-cloak clone of son (WH40k here)? Well that's fantasy. A ship's crew trying to invert a reaction process to vent a certain type of particle stream at an on-rushing astronomical event? Science fiction. That same crew being teleported from one end of space to the other by a magical trickster (Star Trek)? Well that's pretty fantastical.
Fundamentally I think all science fiction HAS to have a bit of fantasy in it...otherwise it'd just be fiction, using current known science to support a story about man vs self, man vs man, man vs ...etc. However, the degree that various offerings of science fiction seem more SCIENCE fiction or science FICTION depends on the individual reading/playing/viewing. Mary Shelly's Frankenstein was science fiction. Does it still hold up as such? Should we now put it into occult fantasy, or horror fiction instead? Is Walking Dead science fiction or science fantasy? What about Battlestar Galactica? To me there are elements of classic fantasy in all of these...as well as some "science" that lumps them into the sci-fi family.
TLDR; To me Science Fiction is the genre, Science Fantasy is the opinion of the reader/viewer/player.