I can only see it as a "situation will dictate" kind of thing, otherwise, am I missing something?
That's exactly it. Knowing how to do something only one way is sure to get you into trouble eventualy.
The way I look at it, if you are behind cover and have the ability to retain the mag, retain it. otherwise just get the gun reloaded. I'm thinking along the lines of a SHTF situation where replacement mags are not readily available like they are in the military.