For a decision-making problem, one MCDA method can be selected based on available information and the nature of the problem. More than one method can also be used and the results compared. Usually the results of all MCDA methods will be similar with only minor differences in the alternative rankings [20].
MCDA methods are often grouped into two general categories: the Value-based methods and the Outranking methods
Value based methods use a rating scale where the lower values represent the least desirable qualities and the higher values represent the more desirable qualities. The range of the rating scales is arbitrary and can be selected to meet the desires of the decision maker . Value based methods include: AHP, DCP, WPM, WSM, Multi-attribute Utility Theory, Weighted Average method
Outranking models compare the performance of two or more alternatives in terms of each criterion, to identify the extent to which a preference for one over the other can be asserted .The preferred alternative tends to be the one that has the highest performance in the largest number of criteria . Outranking techniques are most appropriate when criteria metrics are not easily aggregated, measurement scales vary over wide ranges, and units are incommensurate or incomparable. Outranking methods include: Multi-attribute Value Theory and PROMETHEE