We have settled on Southern Africa and have an itinerary in mind. My husband wants to go with an organized tour group. Normally, we are very independent travellers. I am worried about being with the same people for 2 weeks. I know if you get a nice group, it can be great. But what if we end up with a whiner or two? I want to go with a company that will help us plan a more "custom" trip. In that case, we would be going out with the guides at each camp.
Have any of you tried both approaches? Any words of wisdom?

We've done both. One group was led by a friend and most of the participants where known. The other was a tour organized by Zoo Atlanta. My experience is that tours organized by Zoos are good. The cost will include some donation to the Zoo. We did polar bears in Canada with the NC Zoo.
We've done Southern Africa and are about to do East Africa with a travel agent arranging a more tailored trip. South Africa worked really well. We met lots of interesting fellow travelers in the camps and felt like old friends when we parted company in a day or two! This type trip can either have all transfers arranged in advance or you can do some on your own. We choose the former!
I'll be interested in seeing your other responses, too.
Samcat

samcat, thanks for the reply. I was expecting comments from more Fodorites, but I imagine most people do one type of trip or the other. Sounds like the tailored trip to S. Africa worked out well for you. I think that is what we are going to do as well.
Elena

I have done group tours to other destinations but not to Africa - I love doing it independently and, with a good operator, it's so easy to do. And my husband and I are great travel companions so we are quite happy just the two of us - we enjoy chatting to fellow camp guests where we like them, where we don't, we're not forced into their company for more than a few days (unless we're really unlucky and have the same itinerary and that's not happened yet).

Hi Elena,
We also did a custom trip and everything was pre-arranged and booked ahead of time so no hassles whatsoever and we were still with plenty of other people at the camps which made it interesting. I don't think I would ever take a chance on such an expensive trip being ruined by being in a large group of some sort, or even if it wasn't so expensive!