Having stayed at both, we pick based upon the season. In winter, we stay Jambo as the pool isn't a big part of our vacation, and we like having Mara nearby. In summer, we stay Kidani as the pool is a big part of our vacation, and the Kidani pool, in our entire family's opinion, is far better than Jambo's pool.
FWIW, Kidani does have some quick service items--coffee, soda, they do put some pastries and oatmeal out in the morning, etc., but you can't get a full, hot breakfast like you can at Mara. I have made the walk between buildings in about 5 minutes--it seems longer, but it's not if you have a decent pace (or you can take the van)--but I could see where it could be another 5 minutes if you're staying at the opposite end of Kidani as those hallways are pretty darn long (we've always been close to lobby).