ORIGINAL: Alfred
You are on the right track. It is a trade off between more damage and getting any damage inflicted.
A land device is not killed off outright. First it must become disabled. Then, if a disabled device is struck again, it is destroyed. Left alone disabled devices will become ready devices dependent on
(a) the number of support squads present
(b) adequate supplies on hand
Fatigue and morale does not factor directly into the destruction of devices, but they do impact upon the combat effectiveness of the ready devices. To the best of my knowledge, the size of a bomb has no direct impact on the degree of fatigue and morale of the unit. This is the sort of abstraction I alluded to earlier and why the debate over small or large bombs for use against land targets is, IMHO, largely sterile. It is always a case of horses for courses.
As to the claim that much has been left out of the manual, that is a claim often made, but in my view usually unfairly. For time after time I see posters displaying a lack of understanding of the game mechanics when a careful reading of the manual provides the answer to their posted questions. And what is not found in the manual, and frankly no manual can ever hope to be encyclopedic, can be asked and be promptly answered on the forum.
Alfred
Regarding the manual: Yes - it looks like I've got to get really-really friendly with it. I just had the opportunity to discover airfield limitations. I was getting quite cross with one of my air groups because it wasn't doing what I asked it to do. It took me a little digging to understand that I was giving orders that weren't kosher with the base the air group was assigned to... [:D]
You know, if they made this game manual in similar fashion to the comic-book PM manuals I had when I was in Army boot camp (I could be dating myself here) it would be much more fun to read.
CR