Re the left-handed, right-handed skills. My bro is left-handed and only has to do a journey once to be able to remember it. I'm right-handed and can do a journey ten times and still have trouble remembering all the turns. I don't have any trouble navigating from a map, or from following a list of a route.
I have this theory it's something to do with spatial awareness - he knows where he is in the landscape context. Turn me round twice, and I am lost.