The cars in ProStreet are much faster than real world race cars. Using Willow Springs as an example, ProStreet Zonda can run sub 46 second laps, while real world racing cars (including older Formula 1 type cars) run around 66 second laps.
I'm not sure about RWD versus AWD cars, as opposed to each car in ProStreet is just different. The 911 turbo with stock suspension can run Nevada speed tracks at full speed without going airborne. The Camaro, launched in 5th gear at redline with nitrous is the fastest drag car in the game. The 240SX with stock suspension and tires, is the best drift car.
ProStreet is based on a handicapped points system, not fastest times. Each car has a target time, and besting that target time results in winning points. Some cars are more underrated with target times based on the car being slower than it actually is. For example, for circuit type events, the Zonda is much faster than the 911 Turbo, but the 911 Turbo has a relatively high "handicap", resulting in more points.
