During the Car of Tomorrow era, Sprint Cup models were so close in design that, in many cases, it took a practiced eye to tell a Chevrolet from a Ford and a Dodge from a Toyota.
Consequently, with the cars built to meet common templates across manufacturers, there was little room for Ford Team A to claim that Toyota Team A had aerodynamic or other advantages. The ground for arguments was soggy, at best.
That was then. This is now. The 2013 Gen-Six models actually look like their showroom counterparts. Manufacturer-unique body panels show off the lines of each model.
This is great for fans and, presumably, good for competition, but it potentially opens the door for a game that almost no one likes to play – lobbying for rules changes.