The Python is rightly known as the finest production revolver ever made. This is because of the very high quality standards set by Colt, the care in building the barrel, and the ammount of hand fitting needed to finish it.
The Python uses a slightly different rifling twist, has a tapered bore, and has the mysterious Colt "silver ball" treatment.
For these reasons, the Python is consistently the most accurate revolver around.
The Python uses the very old Colt action that is very complicated, and can be tuned to a high quality trigger action, but can get out of tune if the gun is mistreated, or subjected to a lot of fast, hard double action shooting. The Python doesn't need to be babied exactly, but they don't take abuse too well.
The King Cobra is the last version of Colt's "J" frame revolver that started with the Trooper Mark 3 of 1969. The Trooper Mk 3/King Cobra was to be Colt's "budget" priced gun. Colt could no longer compete with the older Colt revolvers that required so much hand fitting, so they developed the world's first "machine fitted" revolver.
The parts in the KC require much, much less fitting, and was cheaper to make, as well as having a stonger action than the Python.
Accuracy wise, the KC is not as accurate, and doesn't have as smooth an action as the Python. Fit and finish is not up to Python standards, being that it is a "budget" gun.
Unlike the Python, the KC's parts can not be refitted if the action needs repair. Because of the design, parts are simply replaced on the KC.
Bottom line: The Python is up there with Rolex, and Ferrari. The King Cobra is a Honda Accord....Higher quality than other makes, but not a Python.
The Python is world famous as the absolute best. The King Cobra is a hell for strong gun that is a step above most other makers best quality guns.
No less an authority than master gunsmith Jerry Kunhausen thinks the KC may well be the strongest mid-sized revolver ever made.
If you can afford the Python, want the very best, and are willing NOT to abuse the gun, buy a Python.
If you can't afford the Python, want the next best revolver around, and need a super tough revolver, the KC is it.