The 7mm08 is a fantastic round but I would still go with the 243, my friend was in the same situation with his 12 year old so I made a project out of it for myself and researched the hell out of it. In the end I went to every store that sells ammo in Edmonton from walmart to Cabelas to look at ammo availability and price, and the 243 was cheaper, more available, and had a far greater selection of brand names and grains. Even Cabelas and WS only had 2 different kinds of 7mm08 on the self, so if you want the boy to shoot more and not have to travel far for ammo or want to keep ammo cost down go for the 243, Some might argue that the 7mm08 has more "stopping power" or has " better ballistics" and I'm sure they are all probably correct but the 243 is no slouch and has proven itself capable as a deer cartridge and if gets the boy out shooting and he likes it do to the recoil or lack their of then that's what matters. My friends boy loves his 243 and he is one hell of a shot with it also!