This is my home resort and I love them both. Infact, I often flip flop between the two.
IMO, if you are looking for animal viewing and that's super important, I personally think it's better at Kidani. It's also a little more relaxed, layed back feeling. The pool is a bit smaller but that usually equals a bit more quiet but not always. They do the same type of activities at both.
But I will say that Jambo is the reason we fell in love with AKL. It's grand and it is a tad more convienent if you want quick service. You can easily walk to Mara from Kidani in about 10 minutes on a paved pathway or take a shuttle (ask at the front desk) or bus.
If you are driving, Kidani has covered parking. Jambo does not.
If size of room is a factor, Kidani hands down. Even the studios are a bit bigger in Kidani.
You'll enjoy either side of AKL though. You really can't go wrong.