We investigate how expansion geometry influences the unsteady transport in abrupt ${90}^{\circ }$ (step) and gradual ${45}^{\circ }$ (wedge) axisymmetric expansions at step-height Reynolds numbers of 25000 and 35000 using stereo-PIV and time-resolved planar PIV. The analysis follows the evolution of the separated flow from the expansion corner toward reattachment. The strongest dynamical influence of expansion geometry is therefore concentrated near separation and progressively diminishes as the flow approaches reattachment. Near separation, the in-plane spatial spectra are broadly similar, while separation enhances the resolved out-of-plane fluctuation in both geometries and the wedge sustains longer out-of-plane spatial correlations. The streamwise fluctuations exhibit the opposite temporal ordering, with integral time scales of $15$–$18$~ms in the step and approximately $5$~ms in the wedge. Space–time correlations yield $U_c/U_m=0.57$–$0.67$ for the step and $0.75$–$0.95$ for the wedge. The broader step correlation ridges are associated primarily with stronger radial variation of the local convection velocity rather than systematically stronger local decorrelation. Toward reattachment, $U_c/U_m$ narrows to $0.35$–$0.42$, while the differences in temporal persistence and out-of-plane spatial coherence weaken substantially. Short-time FTLE fields and near-wall velocity statistics nevertheless retain geometry-dependent signatures farther downstream.