Well, I doubt the GT will be underrated that much, as much as the Mach anyway. The new GT is a bit heavier. The new GT also doesn't look as aerodynamic as the current stangs. Stock rubber is slightly larger on the current ones (unless you get the 18 inchers, but those are too big for me). I'm sure you'll find examples of each beating the other, but I think the Mach will end up as the slightly faster car. Just for comparisons... a stock Mach 1 ran a 12.88@106 about a month ago. I can't see the new GT doing that.