Hmmmm, started to type a reply about being no difference in the amount of area you could swing over, just the direction.
Then I went and got my bow and figured I'd play around to see what it felt like and make sure before I typed.
Long story short, with either a closed up stance or an open stance, I can cover 180 degrees of shooting without moving my feet or changing my upper body form regardless of how open or closed my stance is. Honestly, to me, foot position is (and SHOULD be) nearly irrelevant. It's all about the upper body and maintaining a solid "T" that does not change regardless of whether I'm shooting to the left, right, inclined or declined. To my thinking, there should be a "natural" draw position where the upper body is strongest and bone does most of the work over muscle. Then you use the universal joint like maneuverability of your hips and legs to aim your entire upper body. Of course, when shooting in the yard or at a range, repeatable accuracy (group shooting) foot position makes things more consistent.
I tend to shoot a less open stance than Asbell shows and it hurts me a little because I have long arms and can pull over 32 inches if I stretch out a little and it's hard to get arrows long enough or spined high enough. The plus to the open stance would be easier availability of arrows and string clearance but I don't generally have clearance issues anyway. I CAN change my draw length by a good 3 inches between closed and open stance. The really open stance feels really strange and seems to require far more muscle effort to draw and anchor than a more normal stance. Real closed feels very solid but looses some of the fluidity and grace of a more moderate, relaxed stance. Can't say I'd bother trying to change now but maybe in the spring I'll mess around with it a little. Or maybe not.
For now, I'll stick to what feels natural. I figure that my natural stance is the most repeatable shot form for ME.