The reason i think tht some people think the Guards should be superior to other Soviet infantry is because of the manpower cost (compared to the other ones) and the name. In reality Guard units were armed with SMGs a lot due to their purpose of Shock atttacks. In reality Guard units were Shock Troops, but they were elite Shock Troops.
Having them equipped with SMGs would make little sense in the begining (because the regular Guards are meant to represent an elite defensive troop, being armed with Medium to Long range SVT-40s and grenades), but the Shock Guard upgrade should add SMGs (any SMG would work PPD-40, PPSH-41, PPS-43, but i think the Fedorov Avtomat would be the best since it would work at all ranges) to at least half the Guards to make them super versitile.
As they stand right now though they are great and effective units, but the SMGs would make them so much better.