It's all been covered above. I have the 32" BC and love it, but I wanted a Buffalo Rifle, not just a .45-70. I have shot both. I don't think either version was more accurate. If I had just been looking for a .45-70 to hunt with, the 22" synthetic (especially the new Handi-Grip stock) would be the way I would go. As stated above, you haven't told us how old/big your son is. I have always felt synthetic stocks mitigated recoil a tiny bit. Factory 400 gr. loads out of a 22" barrel feel just like shooting 20 ga. field loads to me, but I am 6'-2" and 275 lbs. When my son was 7 I started him out with a 20 ga. Handi youth model, no recoil pad. First shot brought tears to his eyes and he didn't want to fire it again. I quickly put a slip-on recoil pad on it, convinced him to try it again, and he never slowed down. It ruined the advantages of the youth stock, but it allowed him to shoot the gun without being beat around. Your son may want a .45-70 because you have one, but a "Different" one so it won't look like he is copying you. Let him get what HE wants, he'll shoot it more. If you need to load some reduced recoil loads for him and don't reload, there is no better way to justify the equipment with the lady in charge than,
It's for the boy"! A Lee Classic Loader is cheap, doesn't require a bench, and is one of the best stress relievers I have found. It is also a nice way to introduce your son to reloading.