Early and mid-war Luftwaffe and Japanese air forces featured many thousands of extremely well-trained pilots who were superb marksmen. During the leisurely years of pre-war training those pilots were taught all kinds of tricks pertaining to marksmanship. For instance, in Poland’s air force PZL P-11 fighter pilots were taught to throw small items (with a streamer or a parachute) overboard, then pursue them while spinning the aircraft and catch them in their gun cameras as they came out of the spin. However, there was no time for practicing such stunts in wartime conditions.
Flying fighters armed with cannon the above-average pilots could hit their targets with no problems despite slow shell velocities and low rates of fire, and inflict grevious damage upon them. However, the same could NOT be told of the 18 year old American airmen who had to be trained by the thousands and fast. For those inexperienced pilots a heavy machine gun in .303 or .50 cal provided the best chance of hitting a target.
The .50cal was the best compromise between rate of fire and hitting power that could be made available to the enthusiastic but inexperienced Allied pilots of WW2.
Rate of fire is absolutely critical which is proven by the time, money and effort that went into the development of rotary Gatling cannons in the 1950s. WW2 cannon shells were deadly, but because of their slow rate of fire it was possible for a target at a very short range to cross right through your frantic cannon barrage without being hit.
I don’t think i would like to be on the receiving end of either. It is interesting to note that even US ground forces were equipped with the quad .50’s for AA defense in WWll. The vision of a P-47 on your tail with 8 fifties spewing lead is devastating to behold. There is some German and allied gun camera footage on Blackwolfs ETO club site that is very revealing. Most of the Luftwaffe film documents engagements with cannon at 500 meters or less! Devastating, you really feel for those bomber crews.
IMO, that would surely depend on the operator of the weapon. Since in an airplane, the pilot is often the operator of both the airplane and the gun, he has to first manuever the plane into a firing position. If an airplane is built around a cannon, it is going to be less manuerverable for flying, but more deadly with shooting. On the other hand, if a manuerable plane is outfitted with a light yet effective weapon to complete its mission then its only objective is reached: target elimination.
So my opinion would have to be based on the particular application for the weapon in the first place. Air to air, air to ground, or both. If I were a pilot of a war plane, and had the luxury to chose between which weapon was given to me, I would then have to go with a plane that is built around a large cannon. I would feel more comfortable attacking armor in an aircraft because of my background in armor identification as an anti-tank/assault demolitions in the Marines. Besides…why choose between a tank and a plane, when you can have both? (A10-A)
[soapbox]