In my younger days, I practiced with both the sling and the staff sling. I never achieved outstanding accuracy with either one. However, I have thrown a river rock as big as my fist through a 3/4 inch piece of plywood at a hundred yards with a staff sling. The stone would whir audibly on its way downrange. The sling requires much time to master and much practice to maintain mastery. But it is fun and quiet.
I would more place it in a role for clandestine hunting for small game in situations where you do not want to attract attention than in an offensive or defensive role.
It has some of the same disadvantages as reloading a muzzleloader.