Published data on the size-specific effective orifice area (EOA) of transcatheter heart valves (THVs) remain scarce. Here, we sought to investigate the intra-individual changes in EOA and mean transvalvular aortic gradient (MG) of the Sapien 3 (S3), CoreValve (CV), and Evolut R (EVR) prostheses both at short-term and at 1-year follow-up. The study sample consisted of 260 consecutive patients with severe aortic stenosis who underwent transcatheter aortic valve implantation (TAVI). EOAs and MGs were measured with Doppler echocardiography for the following prostheses: S3 23 mm (n = 74; 28.5%), S3 26 mm (n = 67; 25.8%), S3 29 mm (n = 20; 7.7%), CV 23 mm (n = 2; 0.8%), CV 26 mm (n = 15; 5.8%), CV 29 mm (n = 24; 9.2%), CV 31 mm (n = 9; 3.5%), EVR 26 mm (n = 22; 8.5%), and EVR 29 mm (n = 27; 10.4%). Values were obtained at discharge, 1 month, 6 months, and 1 year from implantation. At discharge, EOAs were larger and MGs lower for larger-size prostheses, regardless of being balloon-expandable or self-expandable. In patients with small aortic annulus size, the hemodynamic performances of CV and EVR prostheses were superior to those of S3. However, we did not observe significant differences in terms of all-cause mortality according to THV type or size. Both balloon-expandable and self-expandable new-generation THVs show excellent hemodynamic performances without evidence of very early valve degeneration.