I2S Input - Is It Better?

Agree with what Tim said (really good dude). 

Broadly speaking AES/spdif will have a less focus in terms of imaging and staging, but the tend to have a bit more body/warmth. Bass will be a bit more bloated as well. 

I find USB in the middle and i2s on the opposite end - presenting a much cleaner sound but can be lean if your equipment downstream is. 

For a long time, I used a USB cable between my Innous Zenith streamer and PS Audio DSD DAC.  A few years ago, I purchased a Matrix X-SPDIF 2 DDC and a i2s HDMI cable.  I inserted the Matrix between the Zenith and DDC.  There is a very noticeable SQ improvement. 

@snackeyp You should definitely try i2s.

I have a metrum acoustics ambre streamer with spdif, AES and I2s outputs and matching metrum DAC with all of those inputs.  I can easily switch between them and find I2S the best sounding but not by much.  The bass is a little tighter and soundstage a bit larger and the sound a bit more dynamic so I prefer the I2s connection but they are all very good and generally similar sounding so not a deal breaker by any means.