Which is a better truck

It does not matter if the choice is trailduster or ramcharger, same truck. But if he wants a removeable top, would need to get one from the 70's. If that don't matter then get one from the 80's non-removeable top. 80's body style is little different and more replacement parts available than the 70's body style. Pick-ups are the same as body parts, 70's are harder to find. The trailduster/ramcharger are shorter wheel base and would do better on trail rides through the woods. Longer wheel base if he just wants to mud.
But all this is just my opinion.

Badart, them shortened trucks look killer. So doe your OLD truck.