Kidani studios will be about the same size as Jambo studios, they are showing only a 1 sq ft difference, with the exception of the small number of "value" studios in Jambo which are "value" because they are smaller rooms.
As noted Kidani is still an unknown because it is unfinished and no one has been there yet. Jambo, the known, offers top floor (5th most of the building, 6th for concierge area around lobby). You have very good restaurants, Boma a buffet, Jikos with table service, and Mara's with cafeteria style fast service. If you want refillable coffee mugs you can get them refilled at Mara's. The pool area is very impressive and, unlike a normal pool area, it has lots of trees and bushes and thus lots of shady areas you can find to sit in. The savannas are good. Depending on where you are placed, you can have a long walk from your room to the lobby (restaurants, access to pool, store, exit to front and busses, are all near the lobby). Theming is impressive, the lobby is huge, and the main animal viewing area is well done. Part of the being on a savanna theming is a little darkness as colors are dark and you will find that most of the internal of the building is dimly lighted and that actually includes your room. The savannas come very close to the building with the result that there are no first/ground floor rooms, and no exits to the outside except in the front of the building, to the pool area, and to the viewing areas.
Kidani, the unknown, should have very similar theming, will also have a large lobby and a store, the pool on paper looks imprssive as does the new play/recreational area. It will have only one restaurant, which will be table service (they say the pool bar will serve some quick foods) and at this point it is unknown whether you can even do the refillable mug there. You can, of course, use the restaurants and facilities at Jambo but getting from one building to another may be a long walk (1/2 mile from front door to front door). It too will have no rooms on the ground floor and there is supposed to be some parking under the building. The main animal viewing area off the lobby should be excellent. Most rooms will overlook the sunset savanna, which is basically a mess now because of the construction but once that is done it could be the most impressive savanna (part of Jambo also faces it). There will be another much smaller savanna to the very north of the building. I mentioned the possibility of a long walk from your room at Jambo to the lobby. Well, I have seen the north wing of Kidani and this one is going to put Jambo to shame because the walk from rooms at the end of that north wing to the Kidani lobby will be greater than 1/4 mile. Kidani will be all
DVC with the result, unlike at Jambo, that you can get lower floor level savanna view rooms (2d floor). The point: many believe the direct view of the animals you get from the porch of a savanna view room on a low floor is much better than looking down on them from a high floor. Such a request for low floor is not guaranteed. Kidani will have its own bus stop and share busses with Jambo. and will have its own valet service.
I had the same type of questions. When I was planning my trip in Oct. for F&W...I asked member service and they basically told me...if you like being close to the main lobby, Mara, Jiko, Boma...the bus stops then Jambo would be a better fit for you. 
