All I know is I try not to make gearing recommendations for areas in which I don't live or ride. I look at the gearing used by riders that I think are my peers ability-wise (not racers, not genetic freaks, etc.) even if they are in better shape. That tells me what gear range I need to consider and then I determine what components are necessary to provide that range. And a widely spaced cassette just so you can run a double absolutely sucks on flat terrain.
If you're racing, you have a whole different rationale for choosing components.
And if you only ride 50-60 miles distance at most, I don't think you can understand what gears one may need at mile 99.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.