Great video comparison here of the Porsche 911 Turbo Cabriolet against the Audi R8 Spyder.
The problem with physics is that it is largely immutable. Less mass plus more low-end torque and comparable power generally equates to better performance. Take, for example, the Porsche 911 Turbo convertible and the Audi R8 V10 Spyder. As much as we love the design of the R8, it is rather porky at 3,792 pounds. At 3,627 pounds, the Turbo convertible is probably the heaviest 911 ever, but it’s still got a 165-pound advantage over the Audi.
The Audi’s V10 produces 525 horsepower to the 500 hp of the 911, although Porsche’s ratings are generally considered to be conservative. On the other hand, the V10 only produces 390 pound-feet of torque with a peak at 6,500 rpm. The turbocharged and direct injected flat-six of the 911 cranks out 480 lb-ft at just 1,950 rpm.