I dont know whether this argument is balanced, as it depends on how the Cobra or Corvette is prepared for track work, in my opinion the road going Corvette Z06 is one helluva car as far as top speed, fuel economy, handling etc, BUT they are heavy and on a tight track where top speed isnt so important it doesnt surprise me that Scott and Morris can beat them, and some of the Thundersports UK cobra cars would decimate a corvette unless it was a track prepared Le Mans ZO6 like the Aston DB9R it races against and no Cobra is going to even come close to either of those cars due to their aerodynamics speed etc, as displayed on Top Gear with the DB9R doing 1.08 lap compared to the best production supercar at around 1.18 second lap, and I think the 505BHP Corvette did something like 1.22 second lap so I guess if you develop them into a race car anything can happen!!!!!!
As far as road versions go I found this comparison between a 430BHP Cobra and the latest 630bhp Corvette.
http://www.youtube.com/watch?v=LDUTRTd7SMU
http://www.youtube.com/watch?v=YP3WLoZ4Wuo