Depends completely on what the track needs/what vibe I am going for. If I'm trying to make something chill and laid back for example, I'd go funk or even folk. Most Coheed and Cambria (ProgMetal) samples aren't going to exactly set the right vibe for a chill smoke out soundtrack no more than a Crosby Stills and Nash (hippie folk) sample is going to set the vibe for an aggressive street banger. It all depends on what is trying to be done with the music.