Abstract: We present a new system for visualizing and merging differences in diagrams that uses animation, dual views, a storyboard, relative re-layout, and layering. We ran two user studies investigating the benefits of the system. The first user study compared pairs of hierarchical diagrams with matching node positions. The results underscore that naïve dual-view visualization is undesirable. On the positive side, participants particularly liked the dual-view with difference layer technique. The second user study focused on diagrams with partially varying node positions and difference visualization and animation. We found evidence that both techniques are beneficial, and that the combination was preferred.