During our last trip to South Africa in July 2013, we stayed two days in Elephant Plains, Sabi Sands.
It was expensive but we think that it was worth every penny.
I don't know if the guided drives you are talking are the same thing. We had a couple of guided drives in the Elephant Plains part of the Sabi Sands game reserve, we went off-road, came close to sightings that we hadn't seen in Kruger, like Nan said the drivers have constant contact with our driver and inform each other when they had seen a sighting and even use each others position to mark the location of a certain animal one of the jeeps had seen(in our case Leopards).
If I see the amount of money you have to pay for one Game Drive in Sabi Sands, I would recommend one(or two days) in Elephant Plains Sabi Sands(you will get 1 morning drive, breakfast, guided walk, lunch, late afternoon drive and diner per day) for a little more than you will pay for one Game Drive.
If you want more info you may PM me