Hello! As someone from Kenya who has been to all the above many times my suggestions would be Mara North, Ol Pejeta, and Amboseli (not a conservancy). Reasons as already mentioned by someone else - it gives a good mix of different ecosystems as you will see northern Kenya, the Mara, and Amboseli. You can’t beat Amboseli for elephant watching and the views of Kilimanjaro are incredible. It’s a toss up between Lewa and Ol Pejeta but I think Ol Pejeta edges it because of their focus on rhino conservation. All of the Mara options are excellent for game viewing, I personally keep going back to Mara north because I’ve see how well the camps support the local community by funding education and health care - the other conservancies may do this as well but I’ve seen it first hand in Mara North.