As well known, G.Ration is the most important index to measure a abrasives wheels for grinding applications.
G.Ratio = ( A1-A2)/(B1-B2)
Normally we testing flap disc at least 30 minutes non-stop grinding.
General saying, this parameter more big , the flap discs with higher performance in first view . But the hand-feeling, working pressure, etc also need considering.
For example, A flap discs remove 100g work-piece and itself weight reduce 5g, the G.Ratio is 100/5=20. B flap discs remove 200g work-piece and the discs' weight reduce 20g, the G.Ration is 200/20=10. If we can say A is better than B ? The answer is Not absolutely!!! As B remove 2 times work-piece than A and with much higher grinding ability, if considering labor cost, B maybe more economic than A.