I would think if a player decodes a codec to PCM over HDMI they should be nearly the same. Especially from the same company and vintage (no so much from model to model). HD621 is supposed to also clean up the signal quite a bit.

It will be more speed, features and physical build quality that vary more.

- Fiddler (IMHO)

If you think listening to music is fun, try learning an instrument.
HT: G61RSL, 4x5K, 5.5KHC, 2xSC6000, Transporter, HD621, Philips BDP7501 4K, Tivo, 65" LG OLED 4K C6
Computer: Foobar2000, 5K, Mojo, HiFiMan HE1000 V2