I've been on safari in Botswana twice, traveling with Mountain Travel Sobek's on-site contractor, Wilderness Travel, and staying in their luxury camps. Decadent! I went on a safari in Tanzania once, traveling with a pro photographer's company.
I much preferred Botswana. The group was smaller. The biggest advantage was that if our group was on an animal find, other groups couldn't join us for at least 20 minutes. In Tanzania, if an animal was spotted, 30-40 vehicles would rush to that site.