I have stayed at Jambo one time and Kidani two times. I prefer Kidani but I would definitely stay at Jambo again. They both have their positives, the both have nice pools, Sanaa at Kidani is my favorite restaurant. Mara was fine but we never really went there every day when we were there.
Jambo-bigger lobby, bigger gift store, more people, mara, boma, jiko, nice pool
Kidani-smaller lobby, smaller gift store, quieter, sanaa, nice pool
Whatever you decide in my opinion you will be happy, this is the best resort on property!!!