To my mind it doesn't make any difference as long as you are consistent and YOU understand YOUR results. My mind processes things more naturally if I use your first example (highlights are 14, shadows 9 = SBR 5) because that is the way I process numbers in every other instance (something costs $7, I give the clerk $10, I anticipate $3 in change.)

So in my workflow, I place my shadows on Zone III; if the highlights fall in in Zone VII my SBR is 4 and I give normal development. If highlights fall in Zone VIII SBR=5 and I give N-1; Zone VI I give N+1, etc.