These articles are amazing, genius.... i can't wait to read all of them and then re-read all of them again... - Christopher

The article seems to miss that whether a mic/speaker or direct sound is emanating, the ear is going to be used and all its cool features and the brain processes inherent in that, unless we are talking about robots enjoying music. The comparison should instead be the sound that enters the ear in each instance. You would not want a mic to do the processing the ear does because the processing would be doubled with, no doubt, strange results.
Also, even though light moves faster than sound the brain take more, not less time to process vision. Watching the other musician instead of listening is probably not the best choice unless you can perceive the changes more clearly with vision than sound.
I also seriously doubt that we can tell what direction sound is coming from with one ear other than by moving our heads or already knowing how loud a sound should be if we were aimed at it optimally.
I have some hearing loss in one ear. If I put a hearing plug that ear, that mutes it by an additional 33DB, I am pretty close to deaf in that ear in that situation (which I have to do some times because the muscle he was talking about goes nuts sometimes). When that is the case I truly can't tell what direction sound is coming from with my good ear. My guess is that you are picking up some small bit of sound in the covered ear that is providing you with its direction. One ear direction I say is a total myth. Memory of a sound as it changes typically going around ones head may give cues we pick up, but if there is no relative movement history of the sound, I say I highly doubt any direction can be discerned.