The main difference between Cooker at OpenMandriva and Fedora Rawhide ( from my perspective ), is their Cooker comes ready out of the box for a user to do desktop work, with lots of applications ( probably too many ), and codecs, and drivers. It is also focused on KDE Plasma. Their leader, Bero, seems to be really enthusiastic about OpenMandriva. I do not know any other distros easily offering a clang-built iso nor one with a zen-optimised kernel. Also, they only have about 10 people working on it apparently, and all are volunteers. So one should not be surprised that their Cooker branch has far less activity than Rawhide. One thing I do like about Cooker is only one repo.