> I doubt it, as D_A's target is stationary (and could be reduced to GPS coords) while D_B's target is moving.

It's a good point, though I should point out that GPS denial is assumed in those sort of contexts as a first countermeasure so D_A likely has alternative targeting, and that smaller drones can move faster with less energy storage, which itself requires less weight, compounding the benefits of being smaller.

And also the attacker can send 100 drones without any real targeting at all and 10 proper expensive drones and you need to send up 110 defenders which need to be able to track flying drones. Being the attacker will always be easier.

However, D_A is moving, while D_B can be stationary.