Thank you very much, Balderdash! Really helpful... I have a friend who will go to Cambridge for Mphil this autumn, too, but in my field. Then I guess I would apply to Oxbridge Mphil and some others. I also heard the same thing from a Yale professor about their preference for Oxbridge MAs mainly because of the reference letters and student quality. For all, I won't quit applying to US PhD programs, only want to see what's going to happen. LOL
Then again, thanks for sharing. And good luck with Mphil in Cambridge and application!