Kidani is about 1/2 mile walk from Jambo front door to front door. You can take busses between them and there is often a shuttle. As to which one, advantages and disadvantages:
Jambo: all rooms are on fifth floor (except concierge on sixth). All three savannas (including Sunset which Kidani also faces) have giraffes. Some prefer a low floor view for more direct sight line to animals but high floor view gives you more of a panoramic view around the entire savanna. Pool is larger than Kidani but has smaller slide. Has a lot more mature vegitation (trees, bushes) than Kidani pool and thus it is fairly easy to find shade at Jambo's pool area. Jambo has the much larger store and lobby and three restaurants -- Jiko, excellent table service, Boma excellent buffet, and Mara for counter service. Busses to parks stop at Kidani first and thus you can sometimes, although not often, during morning rush at Jambo face issue of not enough seats. Rooms at end of halls are a long walk from lobby (significantly further than the supposed long walk at BWV). Master bathroom in 1BR has combined tub and shower and it is a large step over to get into the tub. Jambo has no dedicated 2BRs, all are combined 1BR and studio.No community Hall at Jambo.
Kidani: 1BRs (and 2BRs) are significantly larger than Jambo's (about 100 sq ft larger). Master bath in 1BR (2BR) has separate tub and shower. They also have extra bathroom. Many dedicated 2BRs with two queens in second bedroom; with rooms on all floors you can request lower or higher floor depending on preference for savanna view. Smaller lobby than Jambo but still impressive. Store is not impressive in comparison to Jambo's. Only one restaurant, Sanaa, which is table service and no breakfast. However, we consider Sanna one of best reataurantsat WDW. No counter service except for limited items at pool bar. Pool, though smaller than Jambo, has much longer slide. The elaborate kids water play area is great for kids. Has a community hall. Most savanna rooms are on Sunset which has giraffes. The small savanna to the north, Pembe, does not. Has the ideal parking situation if you have a car. You park on ground floor under building and with two sets of elevators along each wing, you can always park fairly close to your room. As I mentioned above, there can be a long walk from lobby to room at Jambo. Well, Kidani stands alone as setting the world record for such a walk down an internal hallway and makes Jambo's walk look like a nice short stroll. Walk from lobby to end rooms on North wing is over 5 minutes adult pace (about 1/3 mile); walk to end of south wing is not much shorter (about 1/4 mile). Wise to request room "close to lobby" there, which, if savanna view,automatically puts you on Sunset savanna and puts you close to all amentites.