I think I'll plump for the first book edition of 1950. First of all because it includes a scene with Haddock at the beginning, thus his appearance at the end of the story is not just as out-of-the-blue as in the magazine version.
The sub-plot with the impending war also gives a little extra tension to the story. That aspect has always intrigued me: after all the central plot is about Tintin investigating exploding cars, not actually trying to prevent a war and the fact that he does not take an active role in preventing it (as he did in "Broken Ear" or "King Ottokar") seemed a bit odd. It also gives more credibility to Müller's sabotage.
Also, having a passion for history, I've always enjoyed the scenes in what was then the British Mandate of Palestine and the conflict between the various elements (British, Jews and Arabs), not to mention the humorous confusion over Tintin's double
how I wish Egmont published all the various versions together under one cover!
Has anyone considered starting an online petition or something in order to encourage the publishers to translate the earlier versions of Tintin's adventures?