If you're heading to AKL, both Kidani and Jambo House have excellent locations to view the animals from. At Jambo House, the main look out is the Arusha Rock Savanna Overlook. At Kidani, the main savanna is the Sunset Savanna. Depending on the time of day and weather, you might see zebra, giraffes, hogs, birds, ankole cattle, Wildebeast, eland, and/or gemsbok, plus some others.
Both savanna are amazing and if you go during the day, there is usually a CM (or two) out on the outlooks that can give you a lot of information about the animals you're seeing. I found talking to the CMs very informative and interesting.
In terms of the two different buildings, if I could only choose one, I'd go to Jambo House. I have to admit, some oft he reason I liked Jambo better is that the store is bigger and I felt like there was more to see and do in the lobby and surrounding areas at Jambo.