Digital Audio Output Differences? Is USB Audio Really The Top-notch?

"Legacy" outputs on a server / player are common. For example, Grimm Audio's MU1 is optimized around AES/EBU (and Coax). The Antipodes K50 is around it's AES/EBU as well (including others). 

The receiving component's "optimized" input is critical as well. In other words, you'll get the best results if both components are optimized around the same I/O.

+1 to @sandstone 's post:

USB is used in some better DAC designs that run in asynchronous mode.  Among other advantages, these DACs apply their own internal clock, thus eliminating jitter. 

However, other port types besides USB  have more recently been configured to run in asynchronous mode, including S/PDIF and AES/EBU.

  Also other excellent DACs exist that use completely different approaches and are not reliant upon USB ports. PS Audio, for example, with I2S, etc.

As @sns points out, generally speaking "most dacs optimized for usb these days" is true. I would dig deeper into your Silent Angel "streamer" to see if there is a clear preference in output by the manufacturer / owners / reviewers.

Personally, I would prefer to see a singular approach to maximize BOM for a dedicated / optimized output...however, this is very limiting for the manufacturer as it ’niches’ their product.

Grimm Audio, is an excellent example of this. They have done a fantastic job with AES out, but had to add Coax to suit more users.

I’ve spent the last few weeks considering mid to upper tier servers/players and eventually narrowed my options to those that are singularly focused on USB out since my DAC is, per the manufacturer, optimized for USB.

And if the USB Audio can provide the " best " digital sound quality, then why added other ports? Ain’t that just costing more on the manufacturing end?

BTW, I was careful in my use of "the receiving component" in my initial post, so as not to exclude DDC components (vs. simply stating >>> to the DAC).

If, for some reason your DAC and streamer are not optimized around the same Input/Output then a DDC is a solution should you want to maximize performance.

Other companies do this, but since I am familiar with Denafrips, I’ll use them as an example. Their DACs, per owner feedback, etc. perform very well using the I2S input...which makes a strong point for using Denafrips’ DDCs so that one can use the DDC’s I2S output to max effect and benefit.

Finally, there are advantages to using the same manufacturer's server/player/streamer, (DDC if available), and DAC as they are already optimized to work together.

FYI, the Pro focused manufacturers tend to optimize around AES.