I visited Balule Nature Reserve on my last trip to South Africa. I may as well tell you straight away that the animals are less visible here than at Kruger. However, I did still manage to see hippo, rhino, zebra (though not in large herds), giraffe, etc. Nevertheless, and without wanting to be too quick to draw conclusions – because it's not a zoo here, and luck plays a large part in what you get to see – I did find it quite disappointing.
I have to admit, however, that this is quite paradoxical, because although I've had the pleasure of going on several safaris at some of Africa's most beautiful reserves, it was actually at Balule where I had one of the most wonderful experiences of all my travels. Balule is actually located on an elephant migration route, and some of these animals approached so close that they were just a metre away from us. A simple electric fence around the camp was the only thing keeping us apart. I could feel a rush of adrenaline during this encounter. It was one of those magical moments.
In conclusion, and though it's difficult to predict what you're going to see when you spend a day on safari, opt for Kruger instead.