Well, You don't state how old your son is, nor his physical size and temperment. That said, either gun is would be satisfactory. I do have both calibers, and find that the 257 is a much more "comfortable" gun to shoot- with factory ammo. And it was more than adequate for the 185 lbs...
When I saw it sitting on the rack of the Scheels in Moorhead, I knew it was a nice gun. Just too much gun for me here in ND. After checking prices on Gunsamerica and Gunbroker, I knew it was priced decent. When I read on the AR forums that you'd bought it, and were looking for a barrel band...
I'd like to see a nice 120/125 grain Accubond in 6.5 mm. My "main" gun is a 260 remington, and this'd be just the ticket for our local whitetail population.
SBB