Which type of cable sounds best for Streamer to DAC: AES/EBU or DIGITAL COAX or USB ??

You will find a ton of opinion on this as there are a ton of variables. 
Not all components will have every available connection option. Some components will have weaker or better connections. Just not a consistent arena. It is a good idea to check with the manufacturer.

Coax is usually better than optical for good audio. Basic Toslink will not move hi def streams well. Toslink is mainly free from interference noise that can be an issue with Coax. Toslink can have jitter issues. Coax much less so. If your system is susceptible to noise/interference then it is good to know what is causing it. Bigger and better cables help here for sure. 

I have swapped around many times between aes/ebu - coax and usb and have used different equipment

I have a Bryston sp3/DCS dac+ upsampler+clock in my main system and indeed I can switch at a press of a couple of buttons between aes/coax/usb

Aes/ebu is much better - I would hate to be limited to the lesser options 

But then again you do get people denigrating xlr (better) compared to rca (worse) .... getting it the wrong way round as they haven't really tested.

So people will always disagree for the sake of it.
Just wait for those on this forum who will chime in saying that bell wire is as good as any!

In my setup, too, AES/EBU seems quite a bit better than USB.  I'm connecting an Auralic Aries streamer to a PS Audio Directstream DAC with modest cables (Curious for USB and DH Labs for AES/EBU).  I strongly suspect, though, that Jazzman7 is right.  It depends (on equipment, on cables, etc.).  The PS Audio DAC handles incoming data very differently than the Vega does. 

I asked Bryston, and they recommended AES/EBU to me for improved sound quality over other alternatives.

Ethernet or I2S. You don't want any computer in your audio room