Carlsbad2,
While yes I2S can be carried via an ethernet "like" connection, it is much more common using an HDMI "like" connection. The problem with both, is that I2S has no industry standard pin configuration; but many transports, DDCs and DACs have the ability to configure the pin connections. And yes all things being equal, I would opt for a unit that has I2S connections.
I2S pin configuration seems to be compatible with popular Chinese made products from Musician, Denafrips, Jay's Audio, and Gustard. I use an Audioquest Vodka 48 8k/10k ($400), and a Supra Cables 2.1 8k ($80), and both of them are terrific....and needed no pin changes. In a lower to mid tier system the Supra cable is a great match, but in more revealing systems the Audioquest is my preferred choice.
Higher end streamers (Innuous/Lumin/Aurender) do a great job of handling their input signals, and probably (I have not done a side by side comparison) have less need for something like a DDC. That said, the best connection with a Jay's Audio to my Denafrips Pontus II was I2S, and it was not even close. Same is true between my Iris DDC and the Pontus II DAC.
Part of that (I surmise) is that the I2S serial bus is the internal transport for PCM data within most digital audio products, and I2S connections eliminate the conversion from that protocol between products....streamer uses internal I2S, I2S cable to DAC, and DAC uses the internal I2S to process the data.....no conversion. Connections other than I2S require that the signal be converted (RCA, SPDIF, etc), and then another conversion when back in the DAC to I2S.
Now I am not an electrical engineer, so this is an audiphile's understanding.....not an engineering expert.