Thanks for the responses. It seems like there may be convergence among many designs as they reach the performance limits of the DAC chips they're based on. There may be some outliers going for a specific modification to the sound in the output stage. I'm getting the impression that I'm not hearing differences between dacs because it is a subtle thing compared to things like how a different amp might sound on any given set of speakers. I've definitely heard that effect. Or the same speakers in a different room. I've had situations where I couldn't believe my ears, thought the speakers were broken or something they sounded so different from one room to the next.
Years ago in the 1900s I had a Sony ES CD player that I thought had a flat, lifeless sound to it. Easy on the ears but boring. So I spent $800 for a Theta Cobalt DAC. That was a lot of money for me at the time. The Theta had plenty of oomph to the sound so I was happy with it's added zest. By the early 2000s I compared the Theta to a cheap CD/DVD player's analog output and to my ears the Cheap DVD player bested it. Since the early 2000s either cheap DACs have gotten better than my ears, or they've gotten better than the rest of my equipment, or both.