Originally Posted by SLU_S5
A lightweight flywheel is one of the best mods for anyone who drives their car spiritedly and take the engine to high rpm often and enjoy shifting/heel toe, on the track or street/canyon roads. Once you shift from gear to gear at high rpm with a lightweight flywheel and feel the responsiveness, it would be hard to go back to the heavy OEM setup -- it's like driving with lightweight alloy wheels, then drive with heavy steel wheels.
The major drawback is installation cost -- to throw away a good flywheel for something much better, when it's not yet needed. In your case, that is not an issue.
Most complaints about lightweight flywheels are true but depend on a few important aspects: A) the car/how big the engine is (torque/stall), B) the flywheel type (how light/ friction material).
Complains about stalling when starting from a stop are from cars with weak 4 or 6 cylinders with little torque. Audi V8's (and likely SC V6's) have nearly zero problem with stalling.
The other noteworthy complain is noise. Depending on the flywheel/clutch brand, expect some rattling (chatter) from roughly 1,000-1,600rpm when lugging 2nd, 3rd, and 4th gear -- for example, 2nd gear at 1,000rpm and stepping on the throttle 50% or more. Everything else after that is not much different than typical OEM, dual-mass setup in terms of noise.
For me, installing a lightweight alloy flywheel was one of the best modifications (top 2). I feel Audi added the heavy, steel flywheel to their performance cars to please grandpas/grandmas and other senior citizens who rip through the street at or bellow the posted speed limit.