You guys are somewhat far away from the mark with this discussion. When comparing the destructive capability of an air-to-air cannon armament, a 10% difference in muzzle velocity is insignificant.
Remember, we are not shooting deers with expanding soft-tipped bullets, we are shooting a (mostly) aluminium airframe with very little armor here and there. So the kinetic energy has very little play in the damage caused by a hit. All these weapons are capable of punching a 20mm hole right through the whole structure, and in most cases also throug any armor carried by a fighter aircraft.
But the real question lies in the destructive capability of the explosion of the shell. The ShVak was a magnificiently designed weapon, however you look at it, weight, rate of fire, and muzzle velocity, all very good. But it had lousy ammo, not from the ballistic viewpoint, but from the projectile viewpoint.
For some reason the Russians seemed to use mostly API type ammo (cheapest/easiest to mass produce???) and very rarely explosive shells. This is evident from the experience of Finnish Airforce fighting against La's and Yak's. The AP capability of the slug was generally not good either. Unable to punch throug the seat-armor of a 109 G2 (though only 1mm to spare).
Even the explosive shells were old fashioned TNT filled ones with non-hardened shell. They had dismal fragmentation pattern and low pressure wave.
Compare that to the MG151/20 that had the tungsten cored "Hartkernmunition" API at least occasionally available, and the very high explosive yield "Minengeschosse" commonly used after the start of '43.
The hexogen-filled, thin-walled "Minengeschosse" operated on the principle of generating very high pressure inside the airframe structure, tearing riveting and blowing surface sheeting away, causing massive structural damage. Even the 20mm version was able to down very sturdily built planes like Pe-2 with only a couple of hits to load-bearing parts of the airframe. Only a short burst, maybe 2-3 hits was enough to shear off the rear fuselage of a La-5.
One thing to add, FAF 109 pilots found out, that a La-5 (twin ShVak, no MG's)turning behind a 109 could not pull enough lead to register hits, so a 109 pilot was safe as long as he continued the max constant level turn. The stalemate was usually broken by starting a spiral climb, and climbing until the engine of the La ran out of power at higher altitudes. I remeber reading reports like "I had to go up to 7500m before I could dispose off the La".
