As above, hours will count. 'Hours is hours'! I think it's more about the aircraft than the licence or location.
But is sounds like the validation process is still a joke, just as it was for me in 2008 when I did it. Flying in SA is not much different from flying elsewhere. Certainly, you can take a JAR PPL to the USA fly similar conditions with far less hassle.
A quick lecture on flying in hot and high conditions (if you're planning on flying around Jo'burg), and an explanation of differences with airspace and procedures in SA, followed by a check-ride should be sufficient.
5 year validity? I did the full Air Law exam, multiple skill test flights etc etc in 2008 and mine was only valid for 1 year! But it is a lovely place to fly around.
