It's all about the people and processes that work for people by: Stephen Warrilow
In my view you need both.
But if I had to choose one it would be leadership - because a good leader will always delegate the management and process side.
Whereas a manager - however gifted and however good the processes - without the gift of leadership will not connect or engage with people emotionally - he/she will almost inevitably be task oriented [cos that's what managers do].