Edit: meant to post this to another thread, but it's applicable here too:

The C6 Z51 package is a big package, which includes new springs, dampers, stabilizer bars, tires, uprated brake rotors, unique transmission, and heavy duty steering and transmission coolers. A C6 with Z51 is almost as fast as the C5 Z06 around a track.

If C&D wanted to be fair, they could have compared a non-Z51 with a base 997, a Z51 C6 with a 997 + sport suspension (or 997S), and the C6 Z06 with the 997TT next year or so. But, I guess their whole point and conclusion was preordained: the C6 is more performance per dollar.

I think this is yet another reason why Porsche should never have bothered selling a new 911 with less performance than the 997S.