PayFast over Stripe, on market grounds.
Stripe is the global default and the wrong choice here. PayFast is the dominant South African gateway, supports EFT and instant EFT, how people actually pay, and settles in rand without a conversion step. For an audience of South African students and small businesses, Stripe would have added friction and currency confusion to every checkout. The correct gateway is the one your buyers already trust, not the one with the best documentation.