If the tongue weight is lighter than the load in the bed technically the trailer will yield less wear on the machine...
...keep in mind though that the terrain will most likely dictate which method will produce more wear, for example, if your route has a lot of rocks/roots/etc that the trailer can get hung up on it could put A LOT more stress on the belt and axles versus just putting the load in your bed...
Another variable is the type of trailer, ie single axle versus double axle....also what type of suspension on the trailer will affect the stress on the machine...
My best success hauling heavy loads is by going nice and slow with a double walking beam axle trailer...
...keep in mind though that the terrain will most likely dictate which method will produce more wear, for example, if your route has a lot of rocks/roots/etc that the trailer can get hung up on it could put A LOT more stress on the belt and axles versus just putting the load in your bed...
Another variable is the type of trailer, ie single axle versus double axle....also what type of suspension on the trailer will affect the stress on the machine...
My best success hauling heavy loads is by going nice and slow with a double walking beam axle trailer...