umm.... i think there's some people confused on the benefits.
correct me if Im wrong, but a lighter flywheel has less weight to turn, correct?
so by comparison a standard flywheel is heaver, and therefore harder to turn.
but once its spinning a heavier flywheel will spin longer than a ligher one.
so in terms of acceleration, a lighter flywheel is better. less dead weight to turn = more acceleration = faster rise and fall of rpm
but in terms of being able to hold those revs once you get to the speed you want, a heavier flywheel is better due to inertia. more dead weight to turn = more inertia = more stable speed through rises and falls in the road = more constant rpm.
so as I said above, if you want slightly better response when accelerating, a lightened flywheel is good.
but if you drive a lot on hwy's or anywhere else where you have slopes in the road at speed, then the standard flywheel will be better because of improved economy and more stable revs (a lighter flywheel results in a faster drop in speed, so engine has to chase gears up and down to maintain a set speed).