The weight that is kept on the crank to keep the boost up is negligible and entirely based on what you're doing/size of the turbo. Like Baller said, drag racing seems to be the most obvious situation, but with the way some of these "street" cars have gone lately, I can see where you might want a flywheel with some ass on it. A simple example would be if you're running a 2 liter with a 35r, the LW flywhel would be just fine. Conversely, a 88mm turbo on a Supra would suffer with a LW flywheel. It's all in the setup/turbo size/utility of the car.