I haven't been following this thread too closely, but this is my opinion on things.
For any given car, there are hundreds, even thousands of possible setups. The geometry on these cars is not fixed. Therefore, setup plays an extremely important role in how well these cars handle. For this reason, I think almost any of the competition level touring cars out there today can be setup to be just as fast, or depending on the setup, faster, than the others. Granted, parts used, such as one-ways, lightened parts (mainly driveshafts, outdrives, etc) also can make a difference. This is why cars like the Pro 3 may not be very fast until you have made them into a completely different car.
This is just my opinion on things.