Difference Between the U.S. Theatrical Release and the Director's Cut

Does anyone know the precise differences between the director's cut (which is what is on the Criterion Disc) and the original U.S. Theatrical Release from 1976?

I know that it's 20 minutes shorter, but is it tonally/structurally different as well?

PS

Anyone in the Los Angeles area should note that Quentin Tarantino's New Beverly theater is playing both the director's cut and the original theatrical release on 35mm this month in tribute to David Bowie.