Thanks! I'm curious what the role of white vs brown sugar is in your model. Personally I've taken to using brown sugar in place of white because I like the molasses flavor better...
The type of sugar actually has quite an impact, other than just the color and flavor. Brown sugar results in taller and softer cookies because it's slightly acidic and so reacts with the baking soda. White sugar causes cookies to spread more and become crunchier.