This work compares two ways of annotating semantic relations expressed in prepositional phrases: semantic classes in the Semantic Network of Adposition and Case Supersenses (SNACS), and tectogrammatical functors from the Prague English Dependency Treebank (PEDT). We compare the label definitions in the respective annotation guidelines to determine expected mappings, then check how well these work empirically using Wall Street Journal text. In the definitions we find substantial overlap in the distributions of the two schemata with respect to participants and circumstantials, but substantial divergence for configurational relationships between nominals. This is borne out by the empirical analysis. Examining the data more closely for participants and circumstantials reveals that there are some unexpected, yet systematic divergences between definitionally aligned groups.