The difference between the two is that "prima facie" is a term meaning there is enough evidence for there to be a case to answer, while "Res ipsa loquitur" means that the facts are so obvious a party does not need to explain any more. For example: "There is a "prima facie" case that the defendant is liable. They controlled the pump. The pump was left on and flooded the plaintiff's house. The plaintiff was away and had left the house in the control of the defendant. "Res ipsa loquitur"."