what you earn in score "points" is different than what you earn in perks.
If you are asking about how to earn perks, then that is related to the amount of damage to dish out (actually, it is the amount of damage absorbed by the target). If you drop a 1000 lb on an ammo bunker, you earn the same amount as if you dropped a 500 lb bomb on it. There is no difference, it takes 312 lbs to destroy an ammo bunker, fuel tank, barrack, town building, or radar tower. It takes but a few lbs of damage to destroy a auto ack or manned gun on a field. The guns on naval ships are armored so they take a bit more to knock out. Shore batteries take almost 4000 lbs of ord.
Point being... it isn't about what ord you drop, it is about how much of what you drop is absorbed. Oh... then add in the OBJ modifier for your aircraft too.