If you use either type of card, notify your card issuer before you go that you will be visiting SA (and any other countries en route), so they will not refuse your card - if the computer identifies any abnormal spending out of the UK. SA ( and other countries) have hot spots where cards may "refused" especially where large spends occurr.
This will save you being financially stranded. Take two cards - keep them separate - in case one is "lost".