The Weaver is a great stance of peace officers, more like a street fighting stance.
However, as someone posted, the competition timers don't lie . . . and isosceles is the way to go . . . when one is not having to worry about operating a portable radio, manipulating a tactical flashlight or protect one's self against fists and less than lethal attacks.
When engaging multiple targets to the left, center and right, while moving and using cover. the isosceles stance becomes superior . . . at least for the majority of those who win matches with speed and accuracy.
AS SEVERAL HAVE POINTED OUT THOUGH . . . it is good to practice with a variety of stances . . . practice using either eye . . . practice one-handed, from both hands, etc.
If the SHTF though, you'll want to shoot as accurately as possible . . . in the FASTEST time possible. Folks, unless an attacker is in your face . . . this means Isosceles.