In the end, maybe there is no right or wrong answer, and it's purely a matter of taste.
I love grain in animation because it reminds me of "live-action" films while grainless animation films remind me of cheap TV or direct to video animations.
Between these 2, i certainly prefer (aesthetically) the 2nd!
http://i1.someimage.com/Vk94Vvc.png
http://i1.someimage.com/Rf0gP95.png
Look how the wall, or trees etc., gain texture with grain..