Pounds per horsepower
Divide vehicle weight by horsepower. Lower is stronger. A 3,600 lb car with 400 hp has 9.0 lb/hp. If the same car makes 500 hp, it drops to 7.2 lb/hp.
Horsepower per ton
Horsepower per US ton expresses the same relationship in the opposite direction. Higher is stronger. It can be intuitive when comparing vehicles with very different curb weights.
Why equal ratios can still perform differently
Traction, tire, gearing, shift time, torque curve and aerodynamics can make two vehicles with the same power-to-weight ratio behave very differently. Weight distribution and rotational inertia also matter.
Crank versus wheel horsepower
Keep the measurement basis consistent. Wheel horsepower includes drivetrain losses while advertised crank horsepower does not. Comparing one against the other distorts the ratio.