I'm big fan of Firefly. I was able to do some really good renders. I had good skin shader. I got my render settings working great. But. I haven't used Firefly in over half of year because of the [censored] self shadowing polygon issue. After three scenes that had to be rendered multiple times that problem, I switch to Octane Render.

Superfly is just too slow and very noisy. Also, it doesn't handle HDRI files well. Superfly crashes when uses an HDRI file as the light source and rendering with the video card.