That's not really a fair comparison. I'm not going to sit here and tell you D-S sucks, etc etc. But I will tell you this: now that I have 3 R2R DAC's, I really don't like listening to the NFB-28's DAC anymore. The Sabre has a brighter sound with a more forward treble, which also make it feel more airy. But it's an artificial sound and once you hear it, you can't unhear it.
It's easiest to hear in something like the shimmer after a splash cymbal hit. Instead of a dynamic shimmering sound, it sounds like digital white noise. Think of it like those old "Speak n Spell" toys from the 80s/90s trying to pronounce the "sh" sound. It's just digital white noise because that's the closest it can get. It's close enough for you to understand the intention, but it doesn't actually SOUND like someone saying "sh". Cymbals and such on the Sabre sound like that to me now.
This is one of those things that had to be spoiled for me, though. Had I never heard R2R, I probably would never have noticed. Because of that, I'd happily continue recommending the NFB-28 to anyone looking for a really solid DAC in the price range. I still think it's a very smooth implementation for a Sabre.
Side note: Because I actually don't like listening to the Sabre anymore, I am having a hard time listening long enough to come up with more detailed impressions of the sound differences. But as I'll be writing up a full review of the DAC-19, I'll do my best to power through it at some point. For now, tho, I'm just enjoying the AGD, which I've had for less than a full day.