I practice all three, but my most instinctive is modified weaver, but after watching a video by Rob Pincus, I have conciously used classic weaver with the draw from low ready, and my shot placement and accuracy percentage has increased exponentially.
I used the Iso stance when I shot IPSC matches. I competed for many years, until my knee gave out. Even though the Iso stance presents a bigger target to an opponent it gives me equal far left to far right gun travel without shifting my feet. That's why it worked for me when shooting multiple targets on an IPSC stage. I still use the Iso stance because it feels natural for me.
I haved used the Iso Stance but I have never had good results which is probably me more then the stance itself I work on reflex's. The Iso is good as you said on mutiple targets. I will have to give it more of a chance to see if i can get good results from it.