We supposed that past contradictory findings on the efficiencies of emotion regulation strategies might come from temporal resolution limitations and we proposed the use of a difference index to gain sensitivity for signal differences. 102 participants reappraised, suppressed, or just watched positive or negative images, while experience, expressivity, and physiological arousal were recorded. Reappraisal regulated efficiently negative but not positive experience. Suppression presented opposite results in terms of experience, but was markedly more efficient than reappraisal on expressivity. Dynamic changes were found for physiological arousal. The difference index may be then an effective method for measuring the emotion unfolding and studying regulation dynamics.