DAC connection: which type gives highest fidelity?


Suppose one wants to connect two digital devices, as in a streamer to an outboard DAC or similar.

Which is the highest fidelity connection?  USB, coaxial, or other?

Thanks!
bobbydd
The best is probably up for debate I2S, AES/EBU, etc. The worst, in my experience, is toslink. Your mileage may vary. 
My understanding is that different manufacturers have optimized different connections among the available options.  So it's really impossible to generalize about.
Many high end mfg are combining R2R, multi bits 
or customs dac chips with a high end streamer which inherently has lower noise when properly designed and 2 less cables. 
Bricasti, DCS, Aqua , are just a few high end companies doing this.