[Synchro909]

IMO, this all boils down to how you will use the car. If it is around town, a lighter flywheel is probably better, especially if you drive it like a modern car and it sounds like a lot of you do. All the talk of spooling up faster etc indicates to me that you want to drive it like a sports car. That is not what they were made for
I do a lot of long distance touring on open roads so I stick with a heavier flywheel in that car. In another, which I use for all sorts of things and is more often in traffic, I lightened the flywheel. Horse for courses! Idle is much better with a heavy one and once up to speed, it makes NO difference, in fact, I feel it smooths things out, even at 50mph. Down shifts are easier but up shifts take a little longer - so what!
Drive it like Henry intended, changing up early, drive steady and a heavy flywheel is better. Drive like a modern car and a lighter one suits better. IMO, It takes self discipline to drive the way they did in the day when you're tangling it with modern traffic.