A 'functional-ahtletic stance' implies that the width of the stance has a purpose...
In previous days with much longer, longitudinally stiffer skis we needed all activity (weight,balance, edging, etc.) to the outside ski, and a narrower stance that emphasized a passive inside ski.
Now with skis that are longer when edged than when flat, and stiffer torsionally than longitudinally it benefits us to have both skis tipped the same, and with some pressure to each.
A hip-ish width stance allows us to do this easier than a narrow stance. Shoulder width may be excessive for all but those seeking great degrees of inclination and commitment to the turn (elite racers).
I also agree with the comment that the exact width will be determined by each skiers physique, personal movement patterns, and intentions on skis. Be careful stereotyping genders...I've skiied with many overedbed (bull-legged) chicks, and underedged (knock-kneed) guys...in fact I married one!
Slide-well! and Happy Turkey day to all!