DAC connection preferred?

OK, DAC fans; Do you have a preference for connecting your DAC to a CD Player or transport-- coaxial, optical, RCA, or other? If so, why the preference?
It depends upon how the I/O is implemented. What works best for one combo might not be best in a different setup.
My DAC connection Preferred is PS Audio DAC BRIDGE II with a cross over Cat 6 cable from my Mac Mini. The Bridge changes everything better and is a must have component going forward for me.
This is strictly my opinion, but I have owned many, many DACs and transports and servers.

In Order:

1. AES/EBU (if available)
2. Coax with BNC connection
3. Coax with RCA
4. ATT Glass Fiber
5. Toslink

(The above list is using a proper cable with the proper terminations and impedances).

I have never owned any gear that had Firewire or the I2S interface or any other proprietary connections. Those are "supposed" to be better.
I agree with Onhwy61 - for instance...

I bought a Bifrost DAC with the USB port to stream from my iMac.

In order to mitigate the obvious USB related issues, I tried a couple of USB cables and settled on a double cable that is joined at the DAC
- one cable was for power the other for signal

Even though this worked extremely well, I then decided to try a v-link192 USB-SPDIF converter connected to the DAC via an RCA SPDIF

It was quite clear the USB interface on the Bifrost was inferior to the USB interface on V-link192.

However, the SPDIF input on the DAC appeared to be as capable as the SPDIF output on the V-link192.

The resolution improved dramatically.

My guess is the USB "interface" selected for the Bifrost had more to do with its very sffordable price point

So, I am assuming that between two connected components, similar cost saving measures that may have been applied during their manufacture, may result in similar inconsistent results between their individual digital inputs.

Basically - its a craps-shoot - simply because, the actual circuitry within a components digital interface may offer a different level of performance compared to the component it connects to.

Quite often, the actual "Interface Specification" only identifies a minimum level of performance in order to work.