Like Rikter said, the THX (faces) set uses the same transfer as the Definitive laserdiscs. It's the same films, the same sound mix. The only difference between them is the Definitive LDs are CAV (3 discs per film) and the THX LDs are CLV (2 discs per film.) CAV is known as standard play and CLV is known as extended play. Without going into details, CAV is typically considered to be better.