title_body: Is there a compelling reason to distribute both '.azw' and '.mobi' files?
upvoted_answer: .azw is basically .mobi with the possibility to add DRM. According to the wikipedia article you cited it even has less instead of more features. Since using DRM is kind of pointless if you also offer a DRM free .mobi version, there is no advantage.
  
  .kf8 supports some HTML5 and CSS3 features which the other formats don't. This allows creating more advanced layouts which may be an advantage if you have more than just plain text with chapter marks and headings.