Madikwe is essentially a biggish fenced game reserve, whereas the Timbavati is part of the huge Greater Kruger and borders the KNP itself. Madikwe is malaria-free, and offers pretty much the same game species as Greater Kruger. The game viewing is generally good, but it can get very busy with vehicles having to standby to get their 10-minute turn at popular sightings. It was still farmland as recently as 30 years ago, which is still obvious to the discerning eye. Most visitors won't notice, though.
Johan