Depends a bit what year the KTM is as they had a pretty big engine update a year or two back. I rode a 2014 690 Enduro rather than a Duke, but it's the same engine. It's more powerful, spins up faster and has considerably more urgency to it. It brings out the hooligan in you. But it vibrates more and had one or two noticeable flat spots. As a road bike I'm certain the Duke will be a sportier ride. I liked the KTMs performance but I didn't like the engines character as much as the XTs. (My XT is nicely set up with exhaust, airbox and Kev mods, so rides nicer than a non modified XT). You really would need to ride one to know if it's for you or not.