The goal of this study was to investigate and compare user search activities of 2 discovery tools at an academic library. The implementation of a new discovery tool (Primo by Ex Libris) to replace an existing system (VuFind) provided a unique opportunity to collect transaction logs of both systems and examine user search behavior in an empirical test. Results from a transaction log analysis and a user study of this study have contributed to the understanding of users' search behavior and their preferences and perceptions of the two systems. We find both commonalities and differences between VuFind and Primo for users' interactions. The combination use of the transaction log analysis and user study could be applied to other similar search systems assessments.