I am also fairly new to the braiding world, but I have done a few projects with 'Roo and calf. The biggest difference is strength, because Kangaroo has more strength in the top layer of the hide you can split it much thinner and retain more strength than any other lace. Calf is decent stuff too, but you will definitely break it more than Kangaroo, and it doesn't look as nice IMHO. Also, since calf usually has to be thicker because of the strength issue, it is much harder to make it smooth. I really don't have any experience with lamb or deer, but I hear they are stretchy.
Hope my little bit of knowledge helps.
