This is purely my subjective opinion, but of all the sound work I've done, animation has spanned a much wider spectrum than live action in terms of varying styles. I've found that sometimes animation gets away with things live action just can't... It can be as minimal and sombre as it gets or as over-the-top and exaggerated as possible. Its obvious that animation can do things live actors can not, and therefore you sometimes have fun with things like "Mickey Mouse-ing" (think of when a character sneaks along in an old cartoon and the music follows each step, usually ascending in pitch).
I guess what it boils down to is that, again speaking very generally, audiences tend to go into an animation a little more willing to suspend their disbelief and a little less sensitive to the realism of the sound design. You are right, this may be changing with some of the uber-realistic animation technology we're seeing; but in my past experience I've generally loved working on animations as I get to throw some of my conventions/restraints out the window and just play with building an atmosphere from scratch!
Hope that helps somewhat!