SD v Tuono BHP

Given the similar engine sizes why is there such a big difference in the actual BHP produced from the SD,

I think the answer is in the origins of the Tuono, it is after all, a Mille without a fairing. The motor is tuned for peak horsepower like a sportsbike, with all the power being made at the top end. The SD was designed to have flat bars and no fairing, so the power/torque is made lower down the rev range, where it's more usable for this type of bike, at the expense of top end.