Using a heavier flywheel will have the same effect. By adding the tungsten inserts you are not magically improving crank balance but merely increasing the rotating weight and the damping effect.
I see these tungsten inserts as the current "must have", no doubt the fad will pass.
I will disagree here.......I will not divulge all the results of my testing...But I will say with 100% certainty that the slug definitely adds top end power and reduces the vibrations in the engine.......I did multiple dyno tests on several engines..tested without slug, then retested the same day with the slug....Not only did the power after peak improve, there was also a noticeable reduction in the engines harmonics at higher RPM's...Not only did the engine carry power better after peak, it also pulled the dyno several thousand RPM higher before maxxing out....Adding a heavier flywheel has no such effect and showed absolutely zero difference on the dyno....... I wont pretend to know all the reasons why, but I can definitely verify the results with 100% certainty on the dyno....