Each building has there own advantages/disadvantages.
Jambo:
grand lobby
2 TS restaurants
1 CS restaurants
large gift shop
spa area
Kidani:
quieter atmosphere
1 TS restaurant
first bus stop
covered parking
kids pool play area
extra bathroom in non-studio rooms
We've stayed in Kidani once and are staying in Jambo next month. I'll let you know then which one I prefer.
If you getting a savanna view room, you may want to consider this:
Kidani is completely DVC. Jambo is only DVC on the top 2 floors. So at Kidani, you have the potential to have a closer view of the animals from your room.
Kidani is wonderful - love Sanaa, love the pool area. That being said, I would pick Jambo. I just like having more food options right at hand and love the bigger lobby and animal viewing areas. Honestly - can't go wrong with either, particularly since they offer frequent shuttle service between the two buildings!
I agree with everything the previous posters have said. I have only stayed at Kidani and am staying for the 2nd time again the 1st week in January. Kidani is newer, with a fabulous pool and a quieter atmosphere. The lack of counter service was my biggest complaint, however we did have a fantastic affordable room service dinner! The resort is gorgeous. My vote is for Kidani.
We stayed at Kidani in 2011 and at Jambo in 2012. I prefer Kidani....the rooms are lighter (in color) and are decorated nicer (IMO). The pool is better at Kidani, but there's no CS. There is a van and a bus that will take you to and from Jambo from Kidani. The lobby is impressive at Jambo, but we spend more time in our room and at the pool than we do in the resort lobby.