A R2R DAC, a MB DAC, tube DAC, a discrete circuit, are harder to get good performance out of, so they usually have more noise, more distortion, and higher cost. Some designs are easier to repair and some might last longer, but that can also go the other way or the same way.
Most of the differences are inaudible, some are audible, all are measurable, all audible differences are easily measurable using Amir's setup.
Why do we have these things then? It is still possible to get good performance, as is the case with this product's amp section. The stories can be interesting. They can be fun to own and see.
Personally I like having more than one horse in the stable, including discrete circuits and tube gear, but the serious gear all uses more advanced technology like chips, opamps, and DS.
I have little interest and no gear with R2R/MB. Not nostalgic, not cool looking, not usually audibly voiced, and not well performing, at a higher cost.