Yesterday, i played a few games and i saw the potential of SU-76. Really great in second line.
But i see that there is not difference between SU76 and AT.
They both do good damage against tank, are bad in classic shot against infantry, and have both artillery to kill infantry, with the same effect.
Of course, the main difference is that AT is composed of infantry, so dont need to be repaired, is hard to be hit by most of the tank, and can be reinforced, can be retaken when loss.
SU-76 is more mobile, can do more miles, but dont have mobile turret, so his position before the fight is more important than all. Like an AT.
So, how do you choose your unit ? depends of the ressources, the map, your tech tree?