Also, OP was taught by a police instructor. Police are very different from civilians. One of those differences is that police wear armor. Isosceles is a great stance for police officers because it "presents your armor" to your opponent. You square off with them to make sure your armor is catching the rounds to your chest. This is a great reason for police officers to use Isosceles, but a terrible reason for civilians
Weaver presents a smaller overall target and allows for easier movement.
But as other posters have said, a bad guy isn't gonna give you time to get into a perfect Weaver stance. You're gonna have to shoot him in whatever position you have to be in at the time. So I just walk around in a Weaver Stance all the time.