I've never played with the ultra stock and forearm, but on the Buffalo Classic the 32" barrel makes for great balance.
I like having the longer barrel with the 45-70 for history sake, but either should serve you well.
Recoil will depend on the loads you shoot. Factory loads are pretty mild on recoil, probably nowhere near a 300 mag.
If you handload you can go from "mild to wild". I've shot some stout loads and they can give you a pretty good kick.
Buffalo Bore ammo makes some loads that are hot, and they can kick like a mule.