Well, there's that, and then too, there's the matter of driving style and "feel". Just as a "for instance", I had both the C6Z06, and the 06SRT Coupe. I found I usually ran about the same times on a road course in both, but felt a bit more comfortable in the Viper; to me, it felt more predictable and consistent. Tony, on the other hand, found the Vette to be "more a point-and -shoot" car on a road course. I'd guess that's a difference in driving style, preferred feel, or maybe both; and that's just it; when the performance is very close (which it is), it's going to come down to what setup a driver prefers. For that matter, you and I might want a pretty different setup in the same car, even if we were running comparable times on a road circuit; that's a good argument for adjustable suspensions, air pressure adjustments, and so on. It's not that one setup or another is inherently superior, just that individual drivers vary in technique.
I agree with you 110%. When I ran in Summit Point, I had a chance to drive an STi and an S2000. My brother drove both cars as well. I was consistently faster by about a second on the STi than he was...but when we ran the S2000, he was about a second faster than I was. He is much smoother than I am ...I am a lot more aggressive. We each would have to set each car differently if we want to get the most of each of them...