It's important to remember that, although the flywheel/pressure plate absorb some of the engine's torque as they gain rpm, they also return that absorbed energy to the transmission's input shaft as the clutch pulls engine rpm back down. If the engine accelerates from a given rpm and is then pulled back down to that same rpm, it all ends up a wash as the amount of energy absorbed equals the same amount of energy returned.
If you are launching your car from a lower rpm than you are crossing the finish line with, overall more energy is getting absorbed with the clocks running than is getting returned. In this case lighter flywheel and pressure plate will always be better, as long as the clutch has enough thermal capacity to slip as required and still cross the finish line without damage. Because lighter components absorb less energy as they gain rpm, less energy absorbed makes more overall energy available to accelerate the car.
An exception to the above is when your clutch is so aggressive that it gives you big wheelspeed spikes after the shifts. Big wheelspeed spikes are basically wasted inertia energy that cannot be recovered. If you are throwing away inertia energy in wheelspeed spikes, installing a lighter flywheel will reduce the amount of inertia energy you are throwing away, which will in-turn show up as an improvement on your timeslip.
If you are launching from about the same rpm that you are crossing the finish line with, flywheel/pressure plate weight is not going to matter much as the flywheel/pressure plate are absorbing the same amount of energy over the course of the run as they are giving back. Since the flywheel/pressure plate weight isn't going to have much affect on your ET, it might be wise to go with slightly heavier components if that added mass gives you more of a safety margin against incurring heat damage.
If you are launching from a higher rpm than you are crossing the finish line with, you may benefit from a heavier flywheel/pressure plate. You still need to gear the car to make the most of your engine's power range, but if the engine is capable of spinning well past its power range, you should take advantage of that for launch. Don't go crazy though, as there is a point where increasing gyroscopic effects will cancel out the gain.
Chapter 01- The Basics of Inertia Management
Chapter 02- Calculating Inertia's Effect on Input Shaft Torque
Chapter 03- Clutch Slip After the Shifts... Good or Bad?
Chapter 04- Heavier Cars LESS Likely To Break Transmissions?
Chapter 05- Understanding The ClutchTamer
Chapter 06- Understanding The Hitmaster
Chapter 07- The Basics of Analyzing Dragstrip Data
Chapter 08- Flywheel Weight- Heavy or Light?
Chapter 09- Choosing a Proper Clutch & Pressure Plate
Chapter 10- The Importance of a Clutch Pedal Stop
Chapter 11- What's the Best Launch RPM?
Chapter 12- Do You Need a 2-Step Rev Limiter?
Chapter 13- Traction Problems- Adjust Shocks, Chassis, or Clutch?
Chapter 14- Are "Clutchless" Shifts Right For You?
Chapter 15- Traction Control- Yes or No?
Chapter 16- Apply ClutchTamer Tech to an Adjustable Clutch?
CHANGING THE GAME ON LAUNCHING YOUR STICK SHIFT CAR!!!