title_body: Is there a difference between a manual and an automatic grinder?
upvoted_answer: The most important differences I think, are time and temperature.
  
  I really don't know much technical details about grinders, but as @luser-droog said, friction will create heat and it will affect the coffee (so, motor grinders can be affected by this if doesn't manage heat dissipation well)
  
  And of course, in all cases, time matters; so, time might be a crucial factor for someone.