There is at least some truth to the claim that the Weaver Stance falls apart under stress. There are also cases where cops under stress used the Weaver Stance. Massad Ayoob reported that Ben Grogan used it in the FBI Miami shootout and I saw a video of a cop using it in a shootout somewhere .
Jeff Cooper taught the Weaver Stance partly because it offers better recoil control, something that matters more with a .45 1911 than with a Glock 17 9mm .
Boatman favors the Weaver, saying the Isoceles plants you in place like a human pepper popper . Many others favor Isoceles ( Pincus, Jarrett etc. ) , so the debate goes on .