In the words of Theo Haimann,
Controlling is the process of checking whether or not proper progress is being made towards the objectives and goals and acting if necessary, to correct any deviation.
This being said, the answer to the question is that the comparison of outputs at various parts of the business model of management entails controlling and leading.
It is controlling because it follows the paradigm proposed by Haimann. It is leading because measuring outputs throughout time is a proactive action toward the success of an organization in abiding by what is its mission and vision. When controlling is involved, there is data acquisition and monitoring across the board. This is why it is important for an organization to maintain documentation of everything that is relevant to the betterment of the company's business model.