I'm surprised that HC-110 is leading by a wide margin, since people seldom talk about it here. Must be a lot of closet users. I thought D-76 or Rodinal would be on top.
Actually you would think XTOL would be close to the top, since Kodak's info says that XTOL has the best of everything: best sharpness, best film speed boost, and finest grain. The ideal developer, seemingly; except for "dreaded XTOL failure" and you have to mix 5 liters of it. And of course some prefer the tonality of D-76 or Rodinal.
May the light be with you.