As others have already mentioned, there are just too many variables to get a true picture of what the actual performance of the cars is; for instance: -
1) they're on public roads - so much of it has to do with who is willing to risk their lives and the lives of other road users more (or less). I'm in agreement with others - save the racing for the track, closed runways or test tracks. [There are plenty of people in Ford Econo-box cars, who could claim to have 'blown away' an M5 because I have chosen not to 'race' them when baited on public roads.
2) If Cars are tuned, how can you compare them? It's bad enough when you dyno two stock cars - of the same type - because you'll get differences in RW BHP due to manufacturing tolerances; let alone two different cars, one tuned, one not.
3) Drivng skill - too many muppets out there... enough said on that point.
The older you get - or at least I get - the less I'm interested in proving myself to others or entering into pissing contests (or worse, who has the biggest knob :wink ) and the more I focus on the beauty of the car and what it means to me (ie. power, handling, lust-factor).