I’d research the game native to each region. I think eastern cape south Africa or central Namibia makes the best first safari.
If you decide Namibia, I’d plan your hunt around eland, kudu, gemsbok, hartebeest, springbok, warthog, Hartmann zebra. I like Namibia because it feels very authentic. The country has a small population and the average farm size is very large. Most outfitters will have a high fence primary farm then a lot of surrounding low fence cattle farms to hunt. Pricing is generally higher than South Africa though.
If you decide eastern cape South Africa I’d plan your hunt around kudu, bushbuck, impala, blesbok, springbok, black wildebeest, Burchell zebra. I like Eastern cape because the variety of landscapes. It’s a lot less commercialized than regions like Limpopo, but keep in mind most hunting farms will be fenced but large. The prices are really fair, but the kudu genetics doesn’t match greater kudu further north. If the hunting experience is what you’re primarily after I think eastern cape is best value and a very good experience.
If you decide Limpopo or other regions within driving distance of Johannesburg, I’d base hunt around kudu, impala, warthog, blue wildebeest, zebra. I’d be more careful with this option though. The benefit is less total travel time to reach, but the area is the most developed and game farming is very commercialized. Nearly all farms will be high fenced and many on the smaller side. Not every farm feels authentic/wild. I’d ask a lot of questions to outfitters about the size of properties they hunt, if they have exclusive access, driving time each day to reach different farms, how many hunters they take per year and at the same time. It’s easier to reach, but I find it a lot easier to select an outfitter in eastern cape or Namibia.
I haven’t hunted Kalahari regions or northern cape in South Africa to compare. I’d expect the hunting something of a cross between Namibia and other regions of South Africa.