The interpretation of cosmological redshift as evidence for the expansion of space is a central component of the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological framework. In this paper, we compare FLRW cosmology with a stationary Taub-NUT gravitational-redshift cosmology using redshift-based observables. We discuss three possible discriminants: the Hubble diagram, redshift drift, and astrometric radial velocities. The supernova Hubble diagram is fit with both a Taub-NUT redshift-distance relation and a reference flat FLRW model. The fits show that present supernova redshift-distance data alone do not uniquely distinguish the two descriptions. However, future observations at high redshift (z > 2) may provide an observational means of distinguishing between the two cosmological theories. In addition, redshift drift provides a direct future observational test: expanding FLRW models predict a systematic, nonzero drift, whereas a stationary Taub-NUT model predicts zero cosmological drift for sources at fixed coordinate distance. Astrometric radial velocities are included for conceptual completeness, but quantitative estimates show that they are not practical at cosmological distances.
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