ninja carries all it's power on the top end. The Duc is a very flat torque curve because of it's v twin design. If you are talking about out performing him in real world situations go for the Duc because it has far more tractable power band.
Forget what the dreamer says...tell me one situation where you are over the 4000 rpm range for a sustained period of time without "police interference" The REAL world is stoplight to stoplight or carving up the twisties and tractable power like a Duc has will win every time. Unless you are Freddie Spencer, buy the Duc. Besides, nothing is cooler than the sound of Italian engineering