Discussion plus qualitative not quantitative scores, in simple terms like "Weak" and "Strong" (plus occasional modifiers like "Very"), with no weighting of attributes. Keep the comparison matrix simple and the discussion at a high level of granularity. While that's paradoxical for the analytic person I am, I've come to realize that "net scores" are usually not the point. The real goal and need is to have a multi-party discussion that leads towards consensus, or at least a rational understanding of why product/approach X was chosen over its competitors. In my experience, soft, non-numerical discussions of the choices available have more often lead to that happy (quasi-)consensus than when the numbers come out.
