I've seen it on this forum about one million times: "AWD handles better than RWD"
That couldn't be farther from the truth.
AWD is great in wet, and good on a launch, but that is the only advantages over RWD.
RWD handles far better, launches nearly as well, doesn't suffer nearly as much drivetrain loss (drivetrain loss on an Audi S4, Lancer Evolution, or WRX STI is about 24%!) and does much better on the top end, as well as generally weighing less than the same AWD car.
Let me quickly explain it.
When it comes to handling, you do not want to be glued to the track like a car on rails, you want to be able slide to some extent. I'm not talking about drifting but rather controlled sliding. In a FWD or AWD drive car, when you come into a turn if the car understeers (and on sharp turns it almost always will), you have to brake to correct yourself from going into a wall or off the course, this is bad. In a RWD car you can increase the throttle and induce a slight amount of oversteer and correct yourself without losing as much speed as braking. This is good.
A good driver in RWD car will absolutely dominate a good driver in AWD car on an Autocross track. Some WRX owners are actually converting there cars into RWD drive cars for this purpose.
On the top end in an AWD car, if one of the axles is driving faster than the other, one is actually pulling, or pushing, the other axle. This is bad because it means in reality only one axle is applying power, and having it literally drag the other axle along. Even an extremely small variance between the axles will cause this, and it will happen to every AWD car, as nothing in this world is exactly equal.
On the other hand, the front axle of a RWD car is being pushed by the rear, this is ok though, because the front axle isn't trying to apply power, and doesn't have a certain speed at which it wants to operate at.
Drivetrain loss is fairly self explanatory, an AWD car has to power all four wheels, this comes out to about 24% drivetrain loss for many AWD cars.
Thus an AWD car that makes 450 HP at the crank, will make 342 at the wheels.
A RWD car suffers about 17% drivetrain loss, so an RWD car that makes 450 hp at the crank, will make 391 at the wheels. A difference of almost 50 hp.
Thus a comparison a lot of people like to make, including many magazines is that a WRX STI is fast enough to keep up with a BMW M3.
This is a lesson I've seen hard learned at the drag strip. A bad run (and most of the BMW owners aren't very experienced) with M3 usually results in about a 13.3 run. A bad run with the STI is a 14.0 second run, and a good run, 13.5. The difference is mostly in the drivetrain loss (as well as the powerband differences).