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A major advantage with empirical downscaling over dynamical downscaling it can be relatively easily used for downscaling large ensembles of climate model data requiring only limited computational capacity. The key drawback is that the empirical methods assumes that future relationship between local and large scales remain the same as in the historical climate. Dynamical downscaling, on the other hand, allows for such changes over time. Furthermore, regional models provide internally consistent climate states implying that several variables from the model can be used simultaneously.
References
Kjellström, E., 2004. Recent and future signatures of climate change in Europe. Ambio, 33(4-5), 193-198.