Given the choice, none of the above. SMGs are only good in urban combat, close quarters, and for self-defense. As an offensive weapon in the field they are nearly worthless. I'd far prefer a semi-automatic long rifle or even a quick action bolt action rifle like the SMLE.
It ain't how many rounds go down range. It's how many hit something. Beyond 50 or so yards a rifle is going to be alot more effective than a bullet hose.

This is why in standard German infantry squads only the leader had a machine pistol. He had it for defense not to normally fight. His primary job was to lead not shoot.
The US issued their infantry company a dozen Thompsons (or M 3 grease guns) to issue to the various units as needed since it was recognized for most purposes they were unnecessary.
For the Soviets it was more a matter of mass production and cheapness that led to widespread use of SMGs rather than rifles.