Approval is different than directing/leading though. That Miyazaki has agreed to those dubs means he is content with the final work, not that it is absolutely true to the original -assuming that's what you care about. I have immense respect for Miyazaki as an artist, but without explicit knowledge of his criteria any trust in his approval is mostly blind. He could have a tendency to westernize his works, even if I doubt that is the case.
If you take the Certified Copy argument, which is an interesting one, then you are left with a choice between two equally valid works of art. I would always go for the original one because I am more interested in Miyazaki's directing than Docter's or Lasseter's or any other Western dubber, however good a director he may be. And, now this may be pure prejudice, I feel an original version is more genuine to the movie than a foreign one.
For the American crowd (ie almost everyone) : Do you think Americans tend to be more reluctant to agree to subtitles than foreigners -who often have little choice in the matter ?
NB : It's refreshing to have a discussion about dubbing that doesn't revolve around how impossibly difficult it is to read all those words on the screen as fast as they appear.