Oh man, we totally talked about stuff like this in my science fiction class freshman year, and I completely forget all of it. I do vaguely remember that we discussed how "real" science fiction requires the science-y tech part of it to tell the story. Like, you could take all the space and laser and stuff out of Star Wars and set it in Medieval England and still have the same basic story of Star Wars. Which makes some sense, I think, because say, if you took the Doctor's TARDIS away and gave him magical powers that let him travel through space and time, I'd lean towards calling Doctor Who science-fantasy more than straight-on science fiction (assuming all the alien-y space stuff was still there). Or you can't take the AI tech out of Neuromancer and still have a story because the tech is the story.

But idk, I tend to lump sci-fi and fantasy into one category and then divide it by magic/no magic, so I don't think too deeply about these things. xD AND HALF THE TIME THE "SCIENCE" IN SCI-FI IS LIKE MAGIC TO ME ANYWAY.