I think it depends on which inputs the DAC manufacturer puts the most effort into, but I found running i2S from my Iris to my DAC to be notably superior to SPDIF. From what I’ve read AES/EBU sounds to be close to i2S in performance, but I haven’t compared directly in my system so can’t say. I’m sticking with i2S, but it should be said the HDMI cable should be as short as possible in that application as i2S degrades quickly with distance (my HDMI cable is 6” and no more than 1 foot is recommended). Some DACs are optimized for USB as well and Holo DACs come to mind there, so again a lot depends on how a given DAC is designed. FWIW.
AES/EBU balanced XLR digital transmission vs. coax and I2S
Is AES/EBU better sounding than SPDIF coax and if so why? Also, how does I2S HDMI compare? With my headphone system I prefer I2S by a small margin, but I am interested in what others have found. Interface: Denafrips Iris DDC to Denafrips Terminator II DAC.