Both giftings are needed, but leaders belong at the top. A manager can keep things running but he won't be able to move things forward. In missions and church life, we don't want to stay where we are. We want the gospel to advance. In a large organisation, it would be very easy to become ingrown and feeding ourselves, keeping ourselves happy.
Managers can make that happen.
Leaders, on the other hand, get us out of ourselves and into new breakthroughs. Even their vocabulary reflects this. The greatest problem facing most churches and organisations is that we are not proactive in dealing with the succession of leadership. I spent over 15 years in my first field and saw translators finish their task without a sense of what would follow. They were 40 years old and not ready to start another project under harsh conditions in a primitive village.