bkg
Explorer
Sportscars and motorcycles has discs because of heat generation. Brakes convert kinetic energy to heat. Speed has a greater impact on the amount of kinetic energy than mass. Sportscars and motorcycles can get go very fast. If you understood how kinetic energy works you would've understood that if double the mass, you double the kinetic energy. Double the speed, quadruple the kinetic energy..
So if a truck were to go fast - just to follow your logic - as say in the instance of the xRunner - a sport truck...
Then discs are better... because... speed. Per your statements.
But... since Tacoma's don't go fast, they don't need discs...
I wonder why the Tundra, 4Runner, Sequoia, Landcruiser (for 20 years now), etc... have discs then... they aren't supposed to go fast like sports cars or motorcycles.