It's been almost two decades since that was the popular question. And the typical answer was that it's always about leadership...you know, managers do things right but leaders do the right thing.
But it is dangerous to split the two. Inherent in every job is the need to show confident leadership and, at the same time, the requirement to make sure things get done on time and on budget. You can have both!
First, ask yourself each morning, "What needs to be managed correctly today?" Then build a task and assignment list to get that done.
Second, ask yourself, "How can I demonstrate leadership today that will encourage my team and our customers or clients?" Third, at the end of the day, ask yourself, "Did I focus on what really mattered today?"
You can become a manager who knows how to lead or a leader who knows how to manage. The emphasis is your choice; just don't ignore the other one!