Kenya and Tanzania are both excellent safari countries, and in the case of the Masai Mara and the Serengeti, they share the same ecosystem across a border. So the choice is less about "which has better wildlife" and more about logistics, budget, timing and what else you want to do.
In short: Kenya suits shorter trips and easy access from Nairobi; Tanzania suits longer trips built around the Serengeti and the Ngorongoro Crater. If you have eight days or more, you can do both.
Kenya's main parks - the Masai Mara, Lake Nakuru and Amboseli - are within a few hours of Nairobi, so a 3- to 6-day trip works well.
Tanzania's northern circuit - Tarangire, Lake Manyara, the Ngorongoro Crater and the Serengeti - is more spread out. The Serengeti alone is a long drive from Arusha, so five days or more is better. See our northern Tanzania circuit guide.
Tanzania's park and conservation fees are generally higher than Kenya's for comparable parks, which tends to raise trip costs at a similar accommodation level. Kenya's shorter distances also mean less time and money spent on transfers. Accommodation level still matters more than country - see how much a Kenya safari costs.
The herds are in Tanzania's Serengeti for most of the year and usually in Kenya's Masai Mara from around July to October. If you travel between November and June and want the big herds, Tanzania is the better choice. See our migration guide.
Kenya
Tanzania
Because the Mara and Serengeti are connected, you can start in Kenya and cross overland into Tanzania. Our 8-day Kenya and Tanzania safari does exactly that. You will need entry documents for both countries.
Choose Kenya for a shorter, efficient safari, especially July to October. Choose Tanzania for a longer trip centred on the Serengeti and Ngorongoro, especially outside July to October. If you have time, combine them.
Both are excellent. Kenya is often easier for a short first safari; Tanzania rewards a longer one.
Generally, yes, mainly because park and conservation fees are higher.
Yes, at different times of year - mostly Tanzania, with the Masai Mara usually from around July to October.
Tell us your dates and interests and we will suggest the country - or combination - that fits best.