I was watching TV this morning and saw a few minutes of the (far inferior) American version of this film, and asked myself why I was watching this when I have the original on DVD? So, I put on Spoorloos, and although I've seen it a few times before, it once again grabbed my interest, and I noticed, right away, a few details that make this version far superior to its American counterpart.
First of all, foreign films usually have an advantage to me by casting foreign actors with whom I am not familiar. In this case, by not being a familiar face, the character of Raymond Lemorne came across as even scarier...he looked like a normal guy that I might meet on the street. In the American version, you have Jeff Bridges looking crazy, playing crazy, and ya just know to stay away! Also, I love the running coverage of the Tour De France playing in the background during the scenes where the girlfriend goes missing. It parallels some of the situations that both of our leading guys are going through....and it's cool that Rex is wearing a yellow jersey (like the Tour leader) during those frantic scenes while he looks for Saskia. This yellow jersey, and all the references to Saskia's dream of the 'golden egg' (like Rex asking her to peel the orange, and her golden foam knitting-needle cover) just bring a sense of unity to the whole piece.
Many people here have written about the ending, which I think is brilliant. I was surprised that the American version (which was also directed by Sluizer, by the way) really copped-out on the ending. Rex was really losing it during those 3 years after Saskia's disappearance, and he was no good to his new girlfriend (who says at one point that she doesn't want to be part of a menage a trois), and no good to himself. His obsession had taken him over, and since he was willing to risk it all to find out what happened to Saskia, then he had to lose it all. Not a happy ending by Hollywood's standards, but it made more sense in the story.
So, if you're considering seeing one of the two versions, please do yourself a favor, and go with this one.