I believe that in order to be prepared for upper management, you need middle management experience. Middle management works with both upper management and lower levels of the company. As you mentioned, middle management works to fulfill the vision of upper management. In order for upper management to set the groundwork and vision, they have to understand the company at different levels.I would say my preference would be middle management. I enjoy working and learning from people on different level (i.e operators, techs, engineers, ect). Upper management usually works more with middle management and people of higher status.