Previous research has identified customer satisfaction and customer–company identification as two of the most important concepts in relationship marketing. Despite their proclaimed importance research on their long-term effectiveness is surprisingly scarce. Also, little is known about how competitive actions affect the long-term effectiveness of both concepts. Furthermore, comparative research acknowledging the concepts’ different theoretical roots and illuminating the differences in their long-term effectiveness is lacking. This study makes a first attempt to address these research voids and offers a comparative analysis of the effectiveness of customer satisfaction and customer–company identification in driving important customer outcomes over time. Latent growth analyses of rich longitudinal data from customers over nine measurement points spanning 43 weeks (n = 6930) show that customer satisfaction and customer–company identification have positive initial effects on customers’ loyalty and willingness to pay, but differ in their ability to maintain these positive effects over time. While the positive effects of customer satisfaction decrease rapidly, the effects of customer–company identification are significantly more persistent. Analysis of the moderating effects of relative competitive advertising suggests that customer–company identification is more effective at immunizing customers against competitive actions.