In sum: the Kidani dedicated 2BR wins by a large margin if what you want is the better and more spacious room. The Jambo 2BR wins if your real concern is to have the better outside-the-room amenities, such as its three restaurants including a counter service.
Room differences:
Jambo: the 2BR is a lock-off (combined 1BR and studio), meaning you will have a double door near the front separating the 1B from the 2BR. As a lock-off, the studio and 1BR each have an entry door. Because the second bedroom is a studio, you also get the mini-kitchen with small fridge and microwave. You have a queen and pull-out couch double in the second bedroom. The balcony has a separation wall between the 1BR and studio. The room is about 1075 sq. ft, close in size to 2BRs at BWV, VWL, SSR, and BCV. The master bathroom has a combined whirlpool tub and shower, rather than separate shower, and entering the tub is a high step-over. That bathroom is separated from the master bedroom by a hallway which can seen from the living room. Closet space is barely OK with a stand-alone cabinet that occupies quite a bit of space in the bedroom rather than an in the wall closet. Jambo
DVC rooms are only on the 5th fl (6th for club level).
Kidani: the dedicated 2BR has a single entry door and is about 1173 sq ft, close to 100 sq ft larger than Jambo, with the additonal space added to the living room and master bedroom and bathroom area creating a very noticeable difference from Jambo. It has three bathrooms rather than Jambo's two, and the master bathroom is assessible only from the master bedroom. That bathroom has closet space built into it, and a shower that is separate from the tub (a much preferred arrangement). It has two queens in the second bedroom, and though that bedroom is about the same size as the Jambo studio, you get somewhat more space because of the lack of the mini-kitchen and front door area. The balcony is one long balcony running across the studio, living room, and master bedroom, better for group viewing of the savanna than having the lock-off's separation wall. Kidani 2BRs are on all floors and many prefer lower floor (a non-guaranteed request) for more direct viewing of animals.
Outside-the-room:
Jambo has the much larger lobby and larger and better store. It also has three restaurants, Jiko, a high priced but very good table service, Boma, one of the best buffets on site, and Mara, a good counter service with many tables including some outside approaching the pool area. There is also a very nice bar area that is off the lobby and above the restaurants Kidani has only a table service restaurant with its own small bar, Sanaa, which is excellent but more costly than a buffet and not open for breakfast. Unlike the restaurants at Jambo that have no real window viewing, Sanaa does have tables with window viewing of the savanna. The pool at Jambo is larger than Kidani, with far more mature bushes and trees than Kidani's providing more areas to find shade than at Kidani's pool. Kidani does have the elaborate kid's water play area near the pool and the much longer slide for the pool. Kidani also has a very nice Community Hall, which jambo lacks.
Jambo has elevators near the lobby and then an elevator about halfway down each of the two wings, Zebra Trail and Kudo Trails, that give the building its U-shape. The walk from the lobby to room can be quite long if you have a room towards the end of those wings, longer than the walks to end rooms at Boardwalk. Kidani has unnamed north and south wings with each having three sets of elevators along the wing. Kidani does not have "long" walks from lobby or bus stop to end rooms on the wings; instead they are "marathon-length." There is no hotel in the world (and I mean the earth not just WDW) that has a longer possible walk from lobby to end room down an inside hallway than the north wing at Kidani and the south wing is not much shorter -- members have reported that with smaller children the walk from bus stop to end room on the north wing can be close 10 minutes. If you plan to walk to the end, you might want to bring a tent that you can set up for the night halfway down before finishing the long, arduous journey in the morning. In attempts to avoid those long walks, many started requesting "close to lobby" when reserving. Now, the number that request close to lobby is so large that many do not get it, and, unfortunately, AKV's back-up to a location request not met is to simply place you in any available area, with the result that many of those who request close to lobby end up as far away from it that you can get. Other requests that you might want to consider to differentiate yourself from those requesting close to lobby are close to pool or Rafiki elevator (elevator that gives you shortest walk to pool) which places you not far from lobby on norht wing, or close to community hall or close to Timon elevator (which place you not far from lobby on south wing, with easy access to the bus stop).
If you have a car, Kidani has the advantage there with a parking lot that is under-building on the ground floor, with some just outside the building, running close to the length of the Kidani building, with the result that you can always find a parking space somewhat close to your room (some who have rooms near the end of a wing actually drive to the lobby when they need to go to the front desk or store). Jambo's lot is across the street from the lobby and walk from parking space to room can be very lengthy depending on where you can find a space and location of room.
As far as sharing amenities go, you can go to either building and use restaurants, pools, stores, and viewing areas, but the length is not short if walking. Front door to front door is about a half mile. You can reduce the walk from Kidani to Jambo to about a quarter mile by requesting a room near the Zazu elevator on Kidani's south wing but that will place you a long way to the Kidani lobby and pool. There is also a shuttle that runs between the buildings, and you can take the buses. Park buses run Kidani to Jambo to park, Disney Springs runs Jambo to Kidani to DS.