Excellent we have the stats of all early game vehicles in this post. Although, I found it odd that the Scout car still beats the kubelwagen even though the kubelwagen's dps is significantly bigger.
probably, dmg per shot and accuracy at range plays a huge role. plus m3 has abit more armour to resist rifle fire so m3 still has the edge over the kubel on the offense.
my guess is m3 are used more aggressively and able to get flank shots in that really destroys the kubel, also being able to load units that also increases the overall dps. while the kubel is more like a suppression platform not aggressively looking to flank, partly due to its poor armour that cannot resist infantry fire as well so going close up to make use of its superior close range dps will get it chewed out by infantry fire.