Digital Interconnects - Which one is the BEST ??!!

Ethernet could only be considered if one has dac with internal steamer. Ive seen reviews where external streamer with usb beat ethernet in on streaming dac. This would be case where external streamer superior to internal streamer and dac has very nice usb board.

I believe  OP is asking about cables for digital physical media, with streaming  in play preferences will be much more variable.

Yes, original question in my case is mostly for CD Transport to DAC, CD player to Amp.

+1 Baylinor. Between CD transport and DAC - depends on which is available. I would use I2S over AES, AES over Coax, and avoid optical if possible. 

Between analog output from CD player to DAC choices are RCA or XLR. 'Best' depends on wether both devices are truly balanced or not.  

agree with @mesch 

op's question is only productively answered in the specific case, specific gear - generalities not useful

Thank you all.  My take away is this:. My Amp only has one COAX, one BMC.  Along with a few Opticals which I should not use.  My CD drives each have COAX, but no BMC.  So the solution is to purchase 2  COAX cables, one with RCA both ends, one with RCA to BNC.  Cool.  Thanks!