I think it depends.
DL's SM and Matterhorn have both had upgrades over the past few years, so it depends on when you rode them. Matterhorn has two sides, and the last time I rode it, the two sides were very different from each other. After they replaced the track on DL's SM, it was soooooo smooth, but that was years ago, now, too.
WDW's SM is very rough. I tell people it could rattle your dental work out of your head. I still ride it, but mourn for what it could be, remembering how nice the one at DL was after it's major overhaul. Still miss the old music, though.
So...has anyone ridden all three of them, including both sides of the Matterhorn recently - like in the past year?