Three-dimensional visualizations employing traditional input and output technologies have well-known limitations. Immersive technologies, natural interaction techniques, and recent developments in data physicalization may help to overcome these issues. In this context, we are specifically interested in the usage of spatial interaction with mobile devices for improved 3D visualizations. To contribute to a better understanding of this interaction style, we implemented example visualizations on a spatially-tracked tablet and investigated their usage and potential. In this paper, we report on a qualitative study comparing spatial interaction with inplace 3D visualizations to classic touch interaction regarding typical visualization tasks: navigation of unknown datasets, comparison of individual data objects, and the understanding and memorization of structures in the data. We identify several distinct usage patterns and derive recommendations for using spatial interaction in 3D data visualization.