Volks have almost exactly the same DPS at all ranges compared to Grens. They are slightly more durable (4-men with 0.92 rec. acc. vs 5-men with 1.0 rec. acc.).
I'm pretty sure Combat Blitz is better then Blitzkrieg.
Not sure about the armor bonus though.
EDIT: You can view stats here: http://stat.coh2.hu/
I do know people like to spam the coh2 stats links to prove their point. But what you can't see from those is that game engine does count models and shots = RNG which shots hit and do HP damage.
So more shots = more likely hits on cover fighting and even more on dividing hits on models who have more models on squads. Seen so much USF riflemen 5xmodels taking a beating and only HP bar goes down, but that is because all the models get hits, but don't drop and timely retreat makes them not lose any manpower, compared to units with 4xmodels make them drop models always and much faster.
All this = Model count effect so much on hits received & how many shots you are doing. Reloading/cooldowns effect alot in this too.
This same DPS bullshits is only when laws of averages happens. That is why "Conscripts" are sometimes for people bad, but sometimes they are godly, because they are 6xmodel squads with 6xrifle damage popping and with RNG those salvos can suddenly all hit and for OST that means always atleast 1xmodel down, then you are fighting 3xrifle shots vs 6xrifle shots, which will always in the end make you lose, because the cons can just charge you to short range.
Other bonus is what the models are targeting, with more targets the dps is divided alot more. 4xmodels getting shot by 6xmodels = 4xmodel squad member getting hits alot more which makes them drop a model that much faster even with single model higher dps and when 1 model is down it lowers the dps 25% on them.
But in the end my opinion Volks > Grens, if you want durable infantry that you need in frontlines. If you need dps from backlines Grens > Volks.
Problem for OST they don't have any infantry really that they can just put to frontlines and have same durability like every other faction can. But you can always play around that with combined arms