Sounds about right. On average a half-ton weighs a good 500 to 1000lbs less than a similar configuration 1-ton. That typically gives it a better power to weight ratio, even with an engine that has significantly less hp (like the 5.0L's 360hp vs the 1-tons 385hp).

With that in mind, even with a lower power to weight ratio, the Heavy Duty truck will still tow and haul circles around the light duty truck when the load gets heavy. They're totally different animals designed with a totally different duty cycle in mind. Hence the 6.2L's being tuned differently in the light duty trucks vs. the heavy trucks.