What changes between the two tours
The six-day tour links Tarangire, one stop in the Serengeti and the Ngorongoro Crater. The eight-day tour starts with Lake Manyara and plans two days in the Serengeti. It ends in Tarangire, the day before the airport transfer.
Time in the Serengeti
The Serengeti covers a huge area and needs time. With eight days, days four and five are devoted to it. The listing presents the wildebeest migration as a goal of those days, with no guarantee.
The Ngorongoro Crater
Both tours go through Ngorongoro. On the six-day tour, the descent into the crater takes place on day five, with a picnic near the Lerai forest. On the eight-day tour, the listing offers Olduvai Gorge and a Maasai village as options.
Extending to Zanzibar
Both listings offer an extension to the island, chosen when you book: two days with the six-day tour, four days with the eight-day tour.