I expect to do some of both on most trips, although usually less during the summer when it's hotter in the afternoon hours. As I'm from the states, I like to make the most of my limited time in the park and be out as much as I can.
I always leave camp as soon as the gate opens, and stay out until 9 or 10 o'clock. Then we'll come back to camp for breakfast. After breakfast we'll do another drive, generally driving towards waterholes to see any activity there. Around noon or so we'll come back to camp and have lunch, visit the pool or take a nap or relax around camp. Then head out again around 3-4 o'clock for our afternoon drive.
But this is all dependent on the sightings we see. If we're seeing lots, or if the temperature is cooler, we'll just stay out.
I had one occasion where we spotted some cheetah on the tar road south of satara, just south of the S126. It was mid afternoon and very hot. The cheetah were extremely far from the road and were difficult to see because they were lying in the shade of a tree. We hoped that they would get up and come closer to the road. So our choice was, leave and come back later just before it starts to cool down, but risk the chance that they move and we can't relocate them, or stay with them during the hot hours till it cools down.
We decided to wait them out. So with the car shut off, we endured the heat at watched them from afar. Cars came and went. Many drove by without even stopping. Some would stop or slow, look around for a minute but not see what we had seen, then drive off. And some would pull up and ask us what we saw, and after a little direction they'd find the cheetah. Dozens of other cars saw cheetah they most likely wouldn't have seen if we hadn't stuck around (yes, I'm giving myself a pat on the back).
Two hours of this went by, before it eventually it started to cool down. The cheetah got up from underneath the tree. It was now the moment of truth. Would them come towards the road like we had hoped? Or would they walk away from us and further out of sight? They began moving south, parallel to the road. I turned on the engine and turned around to follow, hoping they would edge closer to the road. And they did, ever so slowly they meandered towards the road. And then as the got 50 meters or so from the road, they turned sharply towards the road, walking directly towards the car. They crossed the road right in front of us and headed off to the other side.
Our afternoon drive during the heat of the day had been rewarded. And while they would have still been there if we'd gone back to camp and come back later, you can never know what will happen, so that's why I prefer to spend as many hours out as I can.
Apologies for getting a little off topic here, I just started typing and couldn't stop.