I guess a very common metric for defining what aspects of a transformation to focus on the most would be the degree of difference between the old familiar form and the new one. I'll consider the usual human to non-human as the starting point but obviously if a basset hound TFs into a lop eared type of bunny they would likely notice many other things before the ears ;)
Thoughts about being a bunny below and the actual short form answer near the bottom: