I can't really help you choose between the two because I have not stayed at Poly yet, however I have stayed at AK-KV and we loved it. The pool area on that side is much better than Jambo because it is always less crowded (we visited both several times), and the kids area there is set up like a really cool splash pad. If you want to go to the Jambo House pool or in general there is resort shuttle that runs every 10 minutes between the two. What I will advise is that you don't bother wasting the extra points or money on the Savannah View room. Is it cool to look out of your window and/or sit on your balcony and see giraffes? Sure, but if you are only planning one resort day, you really won't take much advantage of that option. We stayed in a Savannah View room during out last trip, and found that we were leaving for the parks either before the animals were let out into the Savannah or just as they we were (they aren't out there walking around all day and night). Conversely, we would return from the park after dark so you can’t see them anyway. If you want to view the animals there are plenty of spots throughout the resort to do so, particularly the viewing areas outside of the lobbies at both Kidani and Jambo. Save your points or money and just get a standard view room. A lot of them have partial views anyway…
Keep in mind, my advice is based on our approach to parks, which is to be there when they open and spend all day there. At most we head back to the resort for a short nap. Which means we weren't taking advantage of the Savannah View then either. Unless we had some "use or lose" points, we probably will not book a Savannah View room again. The resort as a whole is phenomenal though, and I highly recommend it.
