I voted i2s, since that is my preferred system (Kali/Piano). But, I also have a Dragonfly USB system that I use in my classroom, a HiFi Berry Plus (i2s) that I maintain for my parents, and a cheapo USB DAC that lives outside for verandering and hammocking.
But also tried USB and in my opinion the SBC used is a major factor in deciding what to use. And offcourse the quality of the DAC used.
One of the most important factors is where the ‘timing’/clocking is done in the chain and USB can be beneficial to do this at the best please near to the D/A circuitry.