Ok... Hrm... So is there a good way to analize the info to see a average of damage inflicted that makes sense if a pilot is mostly using the same aircraft / ordinance then?
On bomber missions, you could use the landed damage message, which is way more consistent. But be aware it's really damage, merely damaged and not destroyed objects (and thus having no influence on game) do count.
I track my own "efficiency" by actually writing down the type and number of objects destroyed. If you are too busy inflight to scroll back and take notes, you could do the same from film afterwards.
You could do the same thing for strikes in attack planes too, where the "landed damage" message does not appear. It's just questionably if you really want to do all that work...
But in the end, it's very much a theoretical matter and not very meaningful at all, even within the limited scope of scoring. The factors bomb size and are object density do distort the 'results' on a massive scale.
Throw a 4k cookie into towns and you appear as master of efficiency with huge gains in damage hit% and damage score points.
Kill the city by skillfully putting the minimum required bomb weight on each square, and watch score 'suffer'...