This is all relative to what you want to experience.
In our summer the bush comes alive with the rains. This stimulates lots of fresh new growth. As a result the summer is known for being more challenging to spot animals due to the increased vegetation. Our summer is a fantastic time to visit to see birds, with many migratory species arriving in Kruger at this time to breed. There are many animal species that time having their young during the summer months because of the increased food and water availability. So this is a great time to see lots of young and new born animals.
Our winter is known for better all round game viewing. This is because the vegetation is dying back due to the cool and dry climate. This decrease in vegetation allows us to see further into the bush. The dry climate and decreasing water availability make the permanent water sources such as dams and rivers a great place to check for animals coming to drink.