At best the pistol may have a better ADS speed. Potentially greater range too but I don't know the appropriate ratios to compare. In the end, all pertinent perks being the same, the SMG should have greater recoil control (aforementioned grip/stock), damage (larger calibur), RoF (assumption based on being a dedicated full-auto), and magazine capacity (drums vs only mags).

The AP receiver is just plain retarded BTW, a lazy method to avoid varied ammo types. It'd be purely in the hands of damge after maxing the OP's upgrades out. I don't have the default (non-perked) stat values but the quantity of upgrades don't matter. Automatic(Rapid) + Hardened + Armor Piercing the following additional mods for the Submachine gun Receiver: The Submachine gun in contrast to the 10 mm Pistol only has these mods: For Comparison, the 10 mm Pistol has the following Receivers (based on Gun Nut): In my opinion the Submachine gun has to few receivers and even the 10 mm Pistol has a better progression towards the upper difficulty settings, despite being the lower level base weapon.

Fallout 4 smg mods