That story is usally heard from Smith shooters. Alot of the time the crane area is mentioned, but the fact that Colt rotates clockwise instead of counter clockwise explains the size difference. Also Colts come out of time is often heard. That is explained in how Colt uses the hand in lockup. This is a rather simple fix and the timing is restored.
Like Mark Twain's death, the reports of Python "weakness" is somewhat overstated.
As for the King Cobra, no less an authority than Master gunsmith Jerry Kuhnhausen's is of the opinion that the King Cobra may well be the strongest mid-frame revolver ever built. He attributed this to Colt's superior forged frames, cylinders, and heat treating.
My personal belief, is that the King Cobra's more massive, simpler action should outlast the 686.
In a reverse of the "weak" Colt, "strong" S&W theory, the 686 has a more intricate,less massive action than the KC.
Not to step on any tender S&W toes here, but S&W's 686 was a response to the more massive Python and Mark III revolvers.
S&W basically copied the Python's cylinder size, and the barrel was as close a copy as they could reasonably get away with.
Admittedly, the Python action doesn't take too well to abuse, but the frame and cylinder are as strong as any mid-frame ever built.