Paypal is for credit card payments. The charge will be in dollars but at the current exchange rate. Result is immediate and you get your eTicket online and via email. Paypal will also send you proof of payment for your reference.
Payfast is used for online EFT into the institution you bank with... wither Absa, FNB, Nedbank & Standard Bank. Result is immediate, you get your eTicket online and a copy is sent to your email. Payfast will also send you proof of payment for your reference.