Well, in my campaigns I would judge that the most damaged air units if conducting interdiction are the TACs. But - as they have different target than the CAS - any comparison is really just a guess.
But when discussing attacking fleets in ports, then my CAS, TAC and NAV all have identical target. Unfortunately, the only accurate statement I can make is that every aircraft type takes so much damage that it becomes necessary to set mission cancellation as low as 10% just to keep some amount of air force capable of bombing. Hence, I can make absolutely no statement about who might be getting damaged most then.
It is definitely the ship AA doing most of the damage. A port strike on an empty port that has only its land based AA inflicts comparatively little damage to the bombers - basically non-noticeable in the course of missioning such battles. This does happen frequently when enemy fleet leaves port, but player's bombers still bomb the port 1 more time anyway (because of so many other things going on same time).
Anyway, UK provincial AA is only up to 6 in some southern ports by late 1939. I have tried several times to first bomb out the AA; and then the fleet. It is a losing proposition compared to hitting only the fleet - even if ground AA is very high - because enemy repairs the knocked out AA rather quickly. So your bombers aren't even fit to attack anything more once the ground AA is zeroed.
The real trick is Germany having 4 NAVs to start this endeavor with. But because of the "accelerated conquest goals" I only had 2 NAVs in their own half-stack to fly with the full stacks of CAS and TACs. Well, that I learned, incurs a whole new problem: The NAV go for the fleet while all the CAS (8) and TACs (4) hit the port only - so resulting in the brand new NAVs being totally trashed after only one bomb run. It needs mixing one NAV with 3 TAC in two of the stacks, and then adding the 2 CAS stacks to get the 16 varied bombers to work together. Just one of those small "paradoxes" this game is full off to keep things challenging.
But while on the topic, there is actually a very long list why this accelerated conquest seems to be highly inefficient. So much is wrong - bombing fleets before proper tech achieved being just one example. Most of the problems are with the techs. The game seems not designed to be doing other than Poland in 1939, France in 1940, SU in 1941; and then German player is supposed to lose, isn't he?
I am guessing, but I think more and more that the "proper time" for Sea Lion is 1940 - soon after Vichy is achieved and the French provinces are repaired.
As regards USA, seems letting their fleets come near Brest is far easier way to destroy them using either U-boats, NAVs... or German CVs if that will be the choice. Probably an invasion of America should wait until the USN is mostly eliminated. However, will be trying it MJF's way cause that is what is happening.