same permissions for system admin and repo admins
I realized the admin of a specific repo doesn't have the same permissions for the repo as the system admin. Actually he might have the same permissions but simply gets directed to a different page and therefore can not change some settings.
To be more specific the system admin when clicking on options->settings gets to /_admin/repos/reponame/edit whereas a normal user with admin privileges to the repo gets to /reponame/settings. Therefore the normal user can not enable the statistics, downloads etc. I think the normal user should have access to the same repo settings as the system admin, even deleting the repository. He is an admin of the repository after all isn't he.