Well six Mosin Nagants are a strong as four Kar-98s, but isn't having six of them a disadvantage here? I mean when you match up a Grenadier in same cover as a Conscript against each other, and just let them fire away at each other, it's most likely that the first model to die is a conscript one. At that point there are 5 Mosin Nagants against 4 Kar 98s, so the Grenadiers will actually have higher DPS at this point. The question is if this will be enough of a difference for the Grenadiers to gain and hold some DPS momentum. If the 2nd conscript dies about at the same time as (or sooner than) the 1st grenadier, then the grenadiers will effectively have had more DPS than the conscript, leading them to win the engagement in the end.
Now the question is of course what really does happen, RNG makes this a little complex. Would love to see some tests on this, but until then I tend to think Grenadiers are at the advantage here.
If there is an advantage to Grens (there isn't) it's incredibly tiny. All of what you said is offset by Gren model numbers. When you crit a gren the squad loses 25% of its firepower, versus 17% for Cons.
It's completely false to think that one is notably stronger than the other.