The only place to fly into from any international departure city is Johannesburg. I suspect they have good Kudu all over RSA, but the biggest as I understand it are in the Limpopo region. South Africa is a very large country with at least three distinct geographic/weather regions, desert in the west and northwest, humid ocean in Natal and plains north and northeast. Each of these areas produce all kinds of animals but each environment produces better animals that are better suited for it. ie bushbuck are very good in the mountains and humid coastaql areas, Gemsbok are the best in the Kalahari desert and Kudu/impala are likely best up inthe thorn of the limpopo region.
Of course all this is based on natural producing animals rather than pure game farm animals which can be produced anywhere and just transported ie Eastern Cape.