Most presentation software uses the slide deck metaphor to create visual presentation support. Recently, canvas presentation tools such as Fly or Prezi have begun to use a zoomable free-form canvas to arrange information instead. While their effect on authoring presentations has been evaluated previously, we studied how they impact the audience. In a quantitative study, we compared audience retention and macrostructure understanding of slide deck vs. canvas presentations. We found both approaches to be equally capable of communicating information to the audience. Canvas presentations, however, were rated by participants to better aid them in staying oriented during a talk.