Board Thread:General Discussion/@comment-24981087-20141018175745/@comment-24145588-20141018190626

They differ in several significant ways. If I remember correctly: To try to capture all of these differences on the page for the "normal" version of each creature would essentially double the size of the page, and make it confusing as well.
 * Appearance
 * Description
 * Cost
 * Breeding time
 * Likes
 * Earning rate
 * Carrying capacity

I disagree with your supposition that once a rare is gone, it won't be back. I expect they'll cycle around occasionally, be available on daily deals, etc. So, retaining the information is probably useful.