If it had to be one or the other, I'd prefer leadership.
You can have someone who is very experienced, but if they show no leadership, and no one wants to follow them, then that experience doesn't really matter!
If you have a good leader, they can admit that they don't have the experience, and can use leadership skills to draw on the experience of others, in a way that values all those involved for whatever skills / experience / leadership they bring to the Group.
It all sounds so easy when it is written down!!
Pip