Kung Fu Panda 3 has the best animation when it comes to quality. It's obvious since it's the most recent one. But the improvement isn't as visible as in the case of Shrek for instance. Compare first Shrek and the last one. The difference is huge. When you compare Panda films, they're all very similar.
However, what I don't like about KFP3 is its dynamics. The action, the dialogues, the movement. It's all weirdly fast compare to previous films. It looks good, but I think that slower tempo works better in Kung Fu Panda franchise.