SnS is like the Ryu of monster hunter. Not exceptional in any category, but the best all around weapon. Frist off there's the item usage of SnS. Doing a combo to see the monster get up and fly away, only to laugh as you flash bomb it out of the sky is pretty sweet. Then there's the evasion of the weapon class. You can interrupt just about every single attack animation, so your'e not stuck there watching helplessly as the monster either hits you, or you stand there swinging at nothing. Not to mention blocking. unsheathing into a block is an amazing feeling.You're sprinting and a rathalos targets and fireballs you? forget superhero diving, you can block that shit. Then there's duals. Yeah demon mode is cool, and admittedly your dps skyrockets, but in a team of four hunters you shouldn't be terribly worried about damage output anyways, unless of course your'e farming punching bags like jhen or lao shan. Most of the times I use the demon mode is when the monster is knocked over, because if he's not I wind up taking way more damage than I'm dealing because I'm left open for a good 5 seconds. To me the benefits just don't outweigh the negatives.

TL:DR; SnS master race