So in summary.....
if you're planning on luggin in the lower rpms, heavier flywheels are better. If the engine needs to change speed frequently, lighter is better.
With a lightweight flywheel I would expect quicker engine speed changes with more vibration being transmitted to the drivetrain, especially at lower rpms.
With standard flywheel, I would expect a balance between light and heavy.
With a heavy flywheel I would expect a smoother idle and low range, a bit quicker starting, but delayed shifting with a manual and it feeling a bit less perky and a bit more powerful. The feel of torque would be higher, the quick accelerations slower.
A tractor would have a heavy flywheel because of the low rpms used, and the generally steady engine speed. Most tractors don't have a gas pedal but instead have a throttle selector similar to a lawnmower.
For city driving I would want a lightweight, for steady state driving or driving in hilly country or driving with a modified transmission with a higher top gear I would want a heavier flywheel.
So one is not better than the other, the standard flywheel is a compromise, and it all depends on your driving needs.
Or you can go electric and thumb your nose at the ICE.
