I've been in Kruger park several times and in different places... As for me I do prefer far northern part of it in Pafuri area. But If you wish to see leopard it's 100% guarantee to stay in Sabi Sabi area. There're mostly up-market lodges there but I'm aware some suitable places there to fit lower budget. Once you decide to visit Kruger again pls let me know) I will give you some advices...