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I have experience both, the difference between and the other that you will notice the most is when shifting, as the RPMs will drop more with the light flywheel so if your turbo is too big you may risk falling under vtec, this was not my case, i went with a lighter than oem but not superlight to help spool recovery on my B series,
for my K20 in my eg (now k24/k20) I wouldn't go with a light flywheel, I use a type R in it, and that one is around 10lbs i believe, is the perfect weight for both N/A and turbo,
K20 are really good when build properly or when you pick the right parts for it, is a pocket rocket in an Eg chassis,
Hope that helps