I assume you're talking about pixel shift on the A7rIII and IV. Pixel shift is superior in resolution to smooth reflection (especially in the IV where it uses 16 samples at 1/2 pixel shifts), whereas smooth reflection is mostly capable of improving shadow noise from averaging multiple frames and maybe a very minor resolution increase. But of course, you can accomplish smooth reflection-like processing in photoshop using multiple pixel-shifted captures on the mk III and IV cameras. Or if you don't need the resolution of pixel shift, just use the built-in intervalometer to take multiple shots and stack them afterwards, doing the same processing that Smooth Reflection is doing. The Smooth Reflection app is quite convenient in that it speeds up your processing time, but it does not accomplish anything that is not possible using photoshop after the fact.