I know with an all in one you eliminate one more box, set of wires, etc. Plus, any usb issues between streamer-dac. BUT, how big of issue is the USB connection between the streamer and dac (assuming you are using high quality cables) in real life?
Cables are only about 30% of the issue…maybe even less…power supplies, external interferences and actual usb implementation also play a big part. AIO options can be worse or better but much depends on attention to the electronics in use. Just because it’s all in one doesn’t necessarily make it better or worse.
It is tough to say because it is personal. Some don’t need to chase improvements, others do. If you can find a situation you are happy with, them stick with that. I got where I wanted to by removing USB from the equation and I did so for less than the cost of my original DAC. Never mind all the extra bits I put in the chain to try to ‘improve’ matters. It is easy to get carried away chasing ideals and you can forget to enjoy music in the process.
A streamer isn’t necessarily connected to a DAC/amp via USB, right? Is the question here whether USB per se diminishes SQ? Why would it? And if it does, wouldn’t it potentially create a new set of problems to move multiple component functionality into an AOI box? The AOI engineers would need to address any potential problems like heat and electrical noise; they might address them well, or badly. So it depends, doesn’t it?
I would back those AOI engineers to do their job reasonably well.
I have started to wonder if a large part of perceived differences with home use are just down to physiological responses in our auditory system to worrying about a problem and then being able relax more after doing something about it.
Everything is built to a price point, no matter how good the engineers might be.