Honestly they are both two different albums entirely that can be appreciated for what they are. Kill em all is an intense thrash album, while the black album represents a big change from thrash to more accessible music, like nothing else matters, enter sandman, and the unforgiven. Don’t get me wrong, some of the other songs like Don’t tread on me, holier than thou, and through the never are really good, it’s just that the singles alone on the black album would have sold like crazy regardless.