M8 is very fast and consistent, especially from a dig. Those traps don't lie, though. 126 vs. 133 is a huge difference. From a roll the GT500 wins every time unless you're talking 10-20mph rolls, where is struggles with traction.
Also, don't forget this GT500 had the passenger seat out and a res delete. So not completely stock.
My biggest complaint with the M8 is the astronomical price and equally astronomical depreciation that comes with these big lux coupes. M8 Comps are $150-160K with options. Lease or buy, why would you get one over a 992 Carrera 4S? The Porsche is actually cheaper in this case, if optioned right.
GT500 is not any better. $90-100K MSRP for a
Mustang is ridiculous. After the current $10-20K markups we are talking about a $115-120K Mustang...