I'm wondering where you learned your automobile knowledge from, or what your "racing experience" is exactly? Regardless, I'd like to clear some myths...
The disadvantages of FWD are mainly the decrease in vehicle handling ability. With more weight over the front of the automobile, the back end tends to become very light. Rear tire traction is decreased and the car may swap ends on icy roads easier. This has been overcome by designers somewhat by placing as much weight as possible further back in the vehicle. Ideal weight distribution is often described as 50/50 front to rear, but FWD cars seldom get near this.
Unfortunately for the front tires, they must transfer all acceleration, steering, cornering, and braking forces to the road. The tires have only a finite amount of grip, so using some of it for acceleration must decrease it in other areas. The rear tires have very little load on them and are basically only along for the ride, hence the tendency to understeer. Though, in wintery conditions having all this weight on the tires powering the vehicle aids in preventing the tires from slipping.
With some of the mechanical parts removed from the front and installed at the rear, vehicle balance and handling are much improved. Using the rear tires for acceleration traction takes the load off the front, so drivers accelerating out of a corner have much more lateral grip. With FWD, you experiance torque steer. RWD is used on all the world's fastest road course race cars and many performance production vehicles for this reason.
Additionally, AWD is what you were thinking of when you mentioned parasitic loss through the drive train, not RWD.