Clark Ashton Smith created much as an evil god might create. He stands high above his Fantasy worlds and he laughs. He laughs at the poor souls who must suffer his realms of terror and beauty. His is a sardonic humor that torments and feels no kinship with those who suffer under his machinations. Robert E. Howard, by contrast, makes you feel the hero’s skin, let’s you live inside it as Conan or Kull or Bran Mak Morn feels the hatred of the enemy, the bite of swords, the wickedness of evil.
I think this is why I sometimes have difficulty getting into Clark Ashton Smith's work. I suspect that if I had encountered Smith about the same time I encountered Lovecraft, at around 10 to 12 years old, I wouldn't have that difficulty. It's probably why it is easier to get into Robert E. Howard's work.