Whichever you prefer. The .com address is slightly more expensive, but you need it if your business is marketing globally and want to project a global image.

A .co.za address is better if you are going to sell your products in South Africa only or if you want to project a South African image. For example, you would register a guest house or wine farm as .co.za, but if you want to export motorcars all over the world, you would probably prefer a .com address.