Of course, this is the same movie file. Quicktime X removes the black bars (I don't mind), but some usable content gets cropped. That doesn't seem to happen on all videos. Only when there are blacks ...
QuickTime player X sucks in mavericks, especially since they partially broke frame-by-frame scrolling. QT player 7 does some of the above but it's inefficient on H.264 files (scrubbing on x264 is ...