I did not compare my gear hooked up to a 761 against the 791. However, I have compared RJ45 streaming DACs against fibre optical and always preferred fibre. So, my preference there is based on prejudice for fibre. The dealer was not impressed by my view on this, but I am going by my ears.
I get what you are saying about the 791. It is an excellent overall unit. I just feel that a better volume control can be found in the super quiet Serene preamp (or Benchmark LA4/HPA4).
I did get a bit of fatigue on the Parasound Persona 9H system I heard the 761 and 791 on. Now I do not think it was the Moon gear, but it made me focus on the top end more than I expected. I think I get more detail out of the Yggi+.
With regards to the Yggi+ OG. I just have a huge appreciation of how great this thing is. It is much better than the $15k DAC that it replaced. It is super detailed without being fatiguing. It maybe is not the deepest soundstage but I do not care about that. I would love to connect the Yggi+ OG into the 791 via XLR and use fibre and do a head-to-head. Fibre has never lost for my ears.