In the context of staged combustion, I understand that burning ox-rich creates complications associated with having hot, high pressure, oxidizer. Some engines, notably the RD-170 and RD-180 family run ox-rich. The wikipedia page for the RD-180 explains this by saying:
The engine runs with an oxidizer-to-fuel ratio of 2.72 and employs an oxygen-rich preburner, unlike typical fuel-rich US designs. The thermodynamics of the cycle allow an oxygen-rich preburner to give a greater power-to-weight ratio, but with the drawback that high-pressure, high-temperature gaseous oxygen must be transported throughout the engine.
However this block isn't cited and I haven't been able to find much in the way of corroborating sources. I have however found some message boards that mention soot buildup offhand, but again, not a lot of further reading that I can find.
Can someone provide a conclusive answer on either the soot buildup, an explanation of where a power-to-weight ratio advantage comes from, or some combination of the two?