I agree with all that's been said. They're both great bikes, the trumpet is perhaps a bit more practical in terms of off the peg accessories (luggage, seats, etc.). It's also a bit softer on the throttle and handling feels a bit more stable, inspires confidence as soon as you get on the thing. It feels quite heavy in comparison to the SD, and the bars feel further forward and lower. The engine is bloody good, really nice to ride fast or slow.
The superduke is more flickable, packs more of a punch on the throttle, meaning you can still get a thrill of riding it without going silly speeds. You don't get the option of decent luggage or touring type stuff without having a bit of a look around first, but there are plenty of cool little bits to spend money on! It just seems a little bit more hilarious to ride. Don't know how to put this, to me the triumph feels like a normal motorcycle, while the KTM feels like someone's stuck a V-twin into a BMX frame.
Both are great bikes, try them both as they're pretty different, comes down to personal preference. The fact I bought a KTM shows which I liked best