No aircraft can be considered the best with the reliability of the Me-262.
As for lethality of weapons, that can be solved by mathematics (not that I did it).
Pk = Ph x Pf where
Pk is the probability of kill.
Ph is the probability of hit.
Pf is the probability of fatal hit.
In English, the probability of a kill is the probability of a hit given the probability of a fatal hit. Let's make this simple. Say the probability of a single hit by a 30mm round is fatal 70% of the time. The hit by a .50 cal. is fatal 20% of the time. Now let's say that the probability of a hit by a single 30mm round is 1%, and the probability of a hit of a single .50 cal round is 2% (higher muzzle velocity). Then, for a single round, the probability of a kill for a 30mm would be .7 % (70% x 1%) or .007, for the .50 cal, it would be .4% (20% x 2%) or .004.
Now, this needs to be calculated over time. Let's assume a one half second burst. For the 30mm, that would be 5 rounds, for a .50 cal that would be 6 rounds. Total amount of rounds fired by a Me-262 would be 20 (4 x 5). For a P-51D, it would be 36 (6 x 6). For a P-47D, it would be 48 (8 x 6). This is based on a rate of fire for the 30mm at 650 rpm, and 750 rpm for the .50 cal. And counting four guns for the Me-262, six for the P-51D, and eight for the P-47D.
Sooo, using the arcane rules of probability, the probability of a kill by the Me-262 with a one half second burst is 1-(1- .007)20 or 13.1%. For the P-51D, the probability is 13.4%. For a P-47D, the probability is 17.5%. It is clear from this example that more smaller guns are better than fewer bigger guns. However, if I changed the variables of probability of fatal hit, this would change to the other way round.
Now, you cannot use any of this a proof in any way. It is all made up. I don't know the probability of a fatal hit by 30mm or a .50 cal. Even the probability calculation is suspect (I couldn't find my probability book, so I had to create the formula. I think it is right), But it does show you the complexity of what you are arguing and, also, if you had the correct numbers for probability of fatal hit and probability of hit (a function, I am sure, of maneuvering, muzzle velocity, and range), you could actually prove which configuration is best. And, most likely, this was done and the weapons were chosen for optimizing the specific configuration for the mission.
Any way, arguing without data is running around in circles. But then, we're good at that!