Personal skill should under no circumstances be ignored in this thread, Krusty.
Personal skill dictates how efficiently and effectively you can use each weapon, or even just attack bombers in general.
I, personally, can use the 30mm. If I can kill a bomber with 4 30mm rounds, and get 4+ 30mm hits per pass, then I have no need to use the 20mm, and sacrafice performance to do so.
Therefore, the K4 is a better bomber hunter and interceptor, for me, than the G-14. Why? Because I don't need 20mm's for hunting bombers.
In addition, you admit that climb and acceleration aid in repositioning, and making another pass. The K4 beats the G-14 in that regard. Quite soundly, above 20k.
K4 has ALL advantages over the G-14, aside from firepower, which is still far more than adequate on the K.
Also, your argument assumes that people will think, reason, and act the same when packing 30mm's as opposed to 20mm's, which is false. People will be aware that they only have 65 rounds, and so will be more conservative with their ammunition.
If people are wastefull with the 20mm's, they won't nessicarily be wastefull with the 30mm, because that 65 displayed on the ammo counter makes them feel like they have little to work with, and so need to be very carefull (not really the case).
And conversely, if you are carefull with the 30mm, you won't nessicarily be carefull with 20mm's, or with .50's.
And I've taken out a bomber with the 109K's 13mm's before. Qartering head on pass, from about ~2 o'clock, holding the 30mm's for a bit closer range (was at D800). I fire the 13mm's, and they go right into the cocpit.
You can kill bombers with .30's, and still have ammunition left over. You can also do so with the 20mm, or the 30mm. Hell, you can do it with the 50mm or the 75mm. Nobody's arguing that. And I don't think anyone is saying that 20mm's are inherently more efficient.
However, I AM saying that PILOTS will tend be more efficient with the 30mm, because they feel they have to count every round.