It is generally accepted that Dugu Qiubai at his peak would annihilate Xiao Feng.
However, Xiao Feng was around 30 years old when he died in the story, while Dugu Qiubai reached his apex after 40 years old.
We know from ROCH that Dugu Qiubai used the Purple Sword before age 30, and he used HIS before 40.
It doesn't mean he was already using HIS at age 30; maybe he started using it at age 33.
But for the sake of this thread, let's assume Dugu Qiubai at age 30 was beginning to use the HIS (maybe not quite perfected yet).
Who do you perceive as being more powerful at the same age?