Model versus man, who is better?

To quote Paul Meehl, an eminent scholar in the field, “There is no controversy in social science that shows such a large body of qualitatively diverse studies coming out so uniformly in the same direction as this one [models outperform experts].”

0. Superiority for mechanical-prediction techniques was consistent, regardless of the judgment task, type of judges, judges’ amounts of experience, or the types of data being combined.
   --Grove et al. 

I was having one of those endless but always enlightening discussions on what is a better approach to investing, a pure model or discretion. Coming from both environments,  I have to say there is value in both based on the type of decision that is to be made and the environment faced. The important skill is knowing when to employ the right decision process at the right time. If you have a lot of data, the model should always do better. If you have a limited data set or limited events, the advantage may be to follow some other decision process. Yet, the a discretionary process may average opinions or use multiple models weighted in some combination. 

In all cases, there has to be a "model" or process in place for how the decision should be made. Process is everything.