I have never considered there were supposed to be gains from the additional cogs. And yet now that you bring it up, I do get very significant gains. I ride in Flatland and use very few cogs to cover my range of speeds. With an 11-speed cassette starting at 12 teeth, I have about 5 useful cogs. With 8 speed, I might have 3. I like the closer spacing. It makes a difference to me.