Is ivermectin as effective, or more effective, than hydroxychloroquine for prevention and treatment of COVID-19?

We would say ivermectin and hydrochloroquine are roughly equivalent in an overall sense, meaning that a similar degree of effectiveness for a group of individuals would be achieved with either agent. The differences will be the variability among individual patients in terms of how they are dealing with the virus, what tissues are under greatest attack and bringing them the greatest risk, as to whether one agent or another might be more advantageous and therefore perform better for those individuals. So this is a nuance that can only be dealt with on an individual basis with more discerning evaluation of the dynamics of the illness in a given patient and a deeper understanding of modes of action. Medicine and science are a long ways from establishing the data needed for such an assessment.