Mercedes ML350 Bluetec - How big a TT can I tow?

Torque determines the ultimate grade you can climb without stalling because its a measure of force.

HP determines how fast you will go, whether tackling grades or air resistance, as it's a simply a measurement of how much work can be performed over a period of time.

Torque can also be multiplied at the transmission and differential (or even at the axle hubs in transit buses and off-road equipment), but HP only gets lost through parasitic loses at each component is passes through.