I cant give you anything definitive, but I recall another member saying that THC tends to be more thoroughly extracted by butane.
They had a very high CBD strain (IIRC there was more CBD than THC), but the resulting BHO was slightly more THC than CBD.
Still higher CBD than you'd get from regular strains, but there seemed to be a preference in the extraction method for THC...
I believe that member had both the bud and bho lab tested, so they weren't just pulling figures out of their ass (like I am now

)