Jaeger,
Your Accord/Altima/Mazda6 comparison is fundamentally flawed because those cars are all the same genre. The compact, two-seat 370Z is a fundamentally different genre from the roomier, four-seat Mustang and Genesis. Comparisons between the 370Z and Mustang are pointless because it consists of the reviewer picking his favorite genre, not the reviewer picking his favorite within a genre. Of course the 370Z's going to be faster and more agile (due to its vastly lighter weight and a chassis with fewer compromises to practicality) and the Mustang's going to be more practical. That's a given. I don't need a MT or Edmunds review to figure that one out.
I posted this thread, not because I gave a rip about what either Motor Trend or Edmunds had to say about Mustang versus 370Z, but because of the really interesting MT review of Mustang GT versus Genesis V6, two direct competitors. The review contradicted a lot of assumptions I (and probably others here) had about which of those two would be the better four-seat sports coupe, and proved how far Ford has come with the latest Mustang refresh.