BACKGROUND: The SAPIEN 3 Ultra RESILIA (S3UR) transcatheter heart valve incorporates RESILIA-treated tissue and new commissural attachments in smaller valve sizes (20 and 23 mm). However, detailed performance data are lacking. OBJECTIVES: The aim of this study was to compare the S3UR with the SAPIEN 3 Ultra (S3U) transcatheter heart valve on the bench for transcatheter aortic valve replacement (TAVR), valve-in-valve (VIV), and redo-TAVR. METHODS: For index TAVR, 23- and 26-mm S3UR and S3U valves were compared at nominal size and during underexpansion. For VIV testing, 23-mm study valves were implanted in 25-mm Epic and 23-mm Mitroflow valves. Redo TAVR involved the implantation of 23-mm study valves in a 26-mm Evolut PRO valve. Hydrodynamic testing assessed mean gradient (MG), geometric orifice area, effective orifice area (EOA), opening index, pinwheeling, and leaflet motion. Histology, light transmission, micrometering, micro-computed tomography, and uniaxial tensile testing compared S3UR and S3U pericardium samples. Leaflet splay area was compared after leaflet modification. RESULTS: For index TAVR, 26-mm S3U and S3UR valves demonstrated comparable performance. In contrast, the 23-mm S3UR valve showed a lower MG (6.7 mm Hg vs 7.3 mm Hg) and larger EOA, geometric orifice area, and opening index than the 23-mm S3U valve, with MG differences increasing during underexpansion. In VIV, the 23-mm S3UR valve demonstrated systolic leaflet fluttering and hydrodynamics similar to those of S3U. In redo-TAVR, the S3UR showed a slightly lower MG and a marginally larger EOA. By micrometering, S3UR leaflet pericardium was thinner than S3U leaflet pericardium (0.28 ± 0.02 mm vs 0.36 ± 0.03 mm), but S3UR pericardium showed significantly higher tensile strength. S3UR leaflets splayed almost 40% less after modification with a central basal split. CONCLUSIONS: Commissural changes in smaller S3UR valves and thinner leaflets drive differences in hydrodynamics, leaflet motion, tensile strength, and leaflet splay after leaflet modification. This warrants further study.