My vote would be for the USSR. Their weapons systems were simple, reliable, and effective. They had no where near the manufacturing capacity and technology of the US, yet they were still one of the most formidable armies in the world.
Come on, Tex, for the first four years of the war they won their victories by sending millions of screaming grunts to their death. It was simply a matter of throwing human meat at the enemy until the enemy ran out themselves. The Soviet leadership didn't start using their brains until the last year of the war. But, still, you make some excellentpoints. And I guess if you look at it from Moscow's perspective, it's better to kill millions of your own than see millions more die under Germany's boots.
And about this M2 vs. MG42 comparison...the M2 was a heavy MG and was not deployed as a standard weapon inthe vast majority of groundunits. The proper comparison between U.S. and German infantry-type machine guns would be the M1919 .30 vs. the MG42.