Serengeti or Masai Mara?

They are the same ecosystem divided by an international border, and the herds move between them freely. The question is therefore not which has better wildlife. It's which suits your trip.

The Serengeti is roughly fifteen times larger. That means more space, fewer vehicles per sighting, longer drives, and regions that are a full day apart. It rewards a longer trip: two nights minimum in one region, three to be unhurried, and eight days or more to see it properly.

The Masai Mara is compact. You can cover a great deal of it in a few days, sightings are dense, and the logistics are simpler. It suits a short trip, and it combines easily with the Kenyan coast or with Amboseli.

For crossings, both work in roughly July to October, because the same river runs through both and the herds cross in both directions.

If you have four or five days, the Mara is the more efficient choice. If you have a week or more, the Serengeti gives you more, and the northern Serengeti in the crossing season is much less crowded than the Mara equivalent.

You can, and a few people do, but it's worth understanding what it costs before deciding.

The two are adjacent on the map and awkward in practice. There is no open tourist border crossing directly between the northern Serengeti and the Mara for vehicles, so the usual routing is a flight, Kogatende to Nairobi or via Arusha, and two sets of immigration, park fees and operator arrangements.

That means a combined trip loses most of a day to the transfer and carries the fixed costs of two countries. On a two-week holiday it's entirely feasible. On ten days it eats the itinerary.

The stronger argument for doing both is that they're different in character, not in wildlife. The Mara for density and conservancy activities like night drives and walking, the Serengeti for scale and for the rest of the northern circuit.

For most people, one country done properly beats two done partially. If the crossings are the goal, choose the side with the better camp availability for your dates and give it three or four nights.

The two differ in ways that show up on a quote as much as on the ground.

Park fees are charged per person per 24-hour period in both, and both are among the higher-priced parks in Africa. Tanzania adds Ngorongoro crater entry if you include it, which is levied per vehicle as well as per person and is the largest single daily fee on the northern circuit.

Access differs more. The Masai Mara is a short flight or a five-to-six hour drive from Nairobi. The Serengeti is a full day's drive or a roughly hour-long flight from Arusha, which itself is an hour from Kilimanjaro International.

Conservancies around the Mara charge their own fees and in exchange permit night drives, walking and off-road driving that the national reserve and the Serengeti national park don't.

Combining the two means two sets of park fees, two operators, and a flight with two immigration crossings. Feasible on two weeks, and an expensive way to spend ten days.