In my understanding a lighter than stock flywheel will give noticeably better accel but only after takeoff. The lighter fw reacts like less torque and requires more rpm to launch to keep from killing the motor. This higher rpm launch will wear your clutch faster and use more fuel.
I would go the route of a freer breathing motor. A good cat back exaust and cold air intake should improve more than the fw and have fewer drawbacks.
just my 2cents