MKSGR:
You believe that a CGT on current production tires would not be faster (or at least as fast) as the Gumpert? Tires are probably the key factor in comparing the various lap times circulation around (including this 7.11...). Of course one could argue that no more up to date tires are available for the CGT or Enzo - which would make the Gumpert relatively more attractive.
To be honest, of all three cars I´d certainly consider the CGT the most attractive for me personally (looks, sounds, performance). However, I´d be surprised if that car would perform better than 7:15 min. with current tires on the Ring, does anybody have performance information for Manthey´s 18" wheel setup on the CGT?
One should not forget that the Gumpert is very heavy (1500 kg) for a car of this type, I assume most of its advantage comes from aerodynamics and uncompromised layout (center of gravity, suspension etc.). After all, Roland Gumpert has played a significant role in Audi´s history of rallycars so he knows what he´s doing.
By the way, I do not think that the Gumpert or the Radical can be fully compared with each other or other sportscars, they have a very constrained focus on performance.