In my system of BDP-1 and non Bryston DAC (both USB and AES inputs), whenever USB is involved at any stage, the sound always gets brighter. Whether it's feeding MPD in BDP-1 via NAS or USB drives, or feeding the DAC via USB from either my computers or even BDP-1's USB. I do have a Jitterbug on the iMac USB output to DAC which reduces the brightness.
As more and more USB is involved, the sound gets livelier/brighter and the plane of the sound moves up. As I continue to reduce USB throughout the sound gets less livelier/brighter and the plane of the sound from which it emerges moves back and the sound gets wider with more ease and space. It's less in your face. I wonder if it's the noise of the USB influencing the sound? Rob Watts of Chord has made several comments about how the sound can change from RF noise and that it can make things brighter which some people might prefer, even if more distorted:
His comments on Jitterbug: https://www.head-fi.org/threads/chord-electronics-dave.766517/page-230
Other compilation post: https://www.head-fi.org/threads/chord-electronics-dave.766517/page-94#post-12262339
With full range music it can be hard to decide what's more accurate or what sounds better. I have flip-flopped many times depending on the day/mood/material. However, when I playback straight vocals without any background music or instruments and just focus on the human voice, the setup with more USB involvement always loses. You can hear this extra glare and body on the voice. However, with full music it can sometimes sound a bit more exciting (at least for awhile). Of course this may be system dependent.