DaVinci Resolve: Difference between adjusting Y or YRGB
My statement that the effect looks the same was incorrect. The use of these sliders is explained in the manual, in "Primary Grading Controls" -> "Color Wheels Palette" -> "RGB Lift/Gamma/Gain Sliders" (page 725 in the v14 manual).  Quoting:


  ... These three controls allow easy Y-only adjustments to contrast, where an increase in contrast results in perceptually diminished color saturation.
  
  Making Y-only adjustments to contrast is a great way to increase contrast when you’re going for muted saturation or a gritty look. This kind of adjustment is also useful in situations where you’re trying to increase shadow density without increasing image colorfulness.