F Ideas: Imagination, Adventure and more rustic (How Come you never see Swords or bows in a SF?)
http://www.imdb.com/title/tt0085811/ (A SF movie which focuses on an item called a krull, a mid-evil weapon of awesome)
Or try star wars. Light sabers (saber being a kind of sword). Wookies use crossbows, and even though these have "energy" they are still the same thing as the midevil ones, just shinier. SW also has Vibroblades (Metal Swords), along with sling shots and other midevil weaponry. Honestly, SF is crawling with sword type weapons. Why? Because swords are cool, being able to see someone (or play as someone) who can cleave an enemy in twine with a flick of his wrist has appeal.
As for the difference in my opinion between the two.
SF: What ifs, that is all it is, what if the world exploded, what if the two cosmic languages were basic and Chinese, what if Kirk was a manly manly man, what if we had lazor guns, etc.
F: Creating an adventure that is impossibly captivating for some reason or another. Almost all elements (Technology and Ideology wise) of a Fantasy book are already known except for what role magic will play, if any. Which limits what they can and cannot do.
I honestly like the works of fantasy that, albeit them rare, has the magician as a scientist, rather than an actual magician. For I too can make fireballs out of air! Science, ya gotta love it.
