There's more than one way to measure shoulder width, and manufacturers sometimes list their bar width as center to center, which could be at the bar ends or a point somewhere in the curve, and others will measure from outside to outside, once again the point of measurement would need to be known. Sometimes it's necessary to surf around to find that information if it's not listed on the manufacturer's site. A typical measurement can be seen here. http://www.ritcheylogic.com/media/Fi...0909lowres.pdf

There are many anatomical differences between us, and we all have varying degrees of flexibility, experimentation is the best way to find out for yourself, if not always practical. For myself, bar width matching the breadth of my shoulders is more comfortable than using a particular muscle insertion point.