Two things...
The tow and payload ratings for 1/2 ton trucks are all over the place so each truck has to be evaluated based on their particular setup. The other issue as far as trucks are concerned is what the numbers dictate versus what you are personally comfortable with. If accelerating or going up hill with the engine screaming at 6K rpm doesn't bother you the XYZ truck may be fine for you and hated by others towing the say rig.
As far as the lighter trailers not being as robust is concerned, I'm not sure that is always true. As weight goes up the forces applied to any load bearing structures goes up but the strength of those structures may not go up proportionally. Maybe someone familiar with the build characteristics can chime in to shed some light on that issue.
