I don't really care what stance someone uses as long as he can make quick, accurate hits and function at the range for hours at a time. I tell students if they want to stand on one foot all day long, that's fine with me if they're comfortable, safe, and get their hits. The reality is that stance is dictated so much by the environment and the situation it's silly to require something rigid for students.
Having said that, I personally use a modified Iso/fighting stance. Or, as a lot of LE instructors like to call it, the Happenstance. Because it's the Stance that Happens when you're under real life-threatening stress. It's not an ideal stance from a pure shooting standpoint, but I'd rather practice what I'm likely to do for real than pretend that my training will overcome thousands of years of instinctive response to danger.