I recall that a type of question like this was asked about teaching. I did not see much of a practical difference in that domain and I don't see that large of one now. From a theoretical point of view, there are differences in the meaning of the words. "Efficient" usually refers to quickness and brisk pace with which work can be done along with a valid use of resources. "Effective" is usually referring to the idea of having an impact, usually positive, on what is being done. I think that in terms of management, both terms are used in conjunction with one another. It's difficult for me to envision an effective manager not being an efficient one. Both principles are needed in order to discover a sense of success in the managerial realms. Effective managers are ones that are able to demonstrate efficiency with actions and decisions. Efficient managers are ones that are able to demonstrate effectiveness with their ideas and beliefs. In the end, both terms are inseparable to the success of the manager.
To understand the difference between an efficient and effective manager we need to understand the difference between efficiency and effectiveness.
Efficiency refers to the ratio of output and input. Higher the output obtained from a given quantity of inputs used, higher is the efficiency. Effectiveness is a measure of the total output. Thus efficiency is concerned with reducing waste and unit costs, while effectiveness is concerned with increasing total output.
We will illustrate this difference between efficiency and effectiveness by an example . Let us consider two production managers. The first manger produces 1000 units of widgets per day at a cost of $8 per widget, while the second managers produces 1200 units of same type of widgets per day at a cost of $8.5 per widget. In this situation the first manager is more efficient than the second one. However, if the widgets sell at price of $12 per widget, and profit on the 1000 widgets produced by first manager is $4000. In comparison the profit on the 1200 widgets produced by the second manager is $4200. As the second manager is able to generate greater profit, he is more effective than the first one.