Picture: 
Sound: 
Extras:
Movie: Picture: Sound: Extras:
Why would this be?
There are in fact some differences between the 2D and 3D versions of this movie that justify this action. The most obvious is that the frames in the 3D version are considerably brighter. That makes sense because any 3D display system requires at least halving the brightness (since each eye is blinded to half the image). In the following, the 2D version is at the top and the 3D version is at the bottom:
There are also some framing differences, although the reasons for this aren't apparent.
Oddly, the left eye view alone of the this movie gets a higher bitrate -- 25.06Mbps -- than the full 2D encode (22.24Mbps). The 3D right eye view gets 14.77Mbps.
Despite the lower bitrate for the 2D version, it was the 3D version's picture quality which had a couple of problems. With the system I was using there was a clear moire pattern in the weave of the green shirt of the chap in the queue at a shop at around 4:30 into the movie. And there were marked jaggies on a light pole at 29:45, but only in the 3D version.
Even though the 3D disc had been programmed not to play in a 2D player, its left eye files (00002.m2ts followed by 00006.m2ts) were perfectly playable on my computer, so I grabbed some frames. It was clear that neither of these defects were in that view on the scene. My suspicion was that these were artefacts due to interference between the two eyes' views upon the scene, with them not being in perfect geometric synch for some reason. But was this because of the disc or the system I was using? That remains unclear.
One other difference: the 2D version gets Universal's 'My Scenes' bookmarks and an enhanced playback mode with seamless branching to visual character commentary sections, while the 3D version gets neither.
This is a good fun movie in the 2D version, and even better in 3D. Watch especially around 49:30 for the roller coaster scene. This is very effective (especially with a 3D projector) but it is unfortunately far too short. Perhaps the movie makers were worried about complaints of little kids toppling dizzily from their cinema seats had this element been extended.
(Australian rating); Region free
The following video bitrate graphs were generated by BDInfo. This is the graph for the main movie stream:
This is the MVC file bitrate graph, which records differences to the master eye:
This is the bitrate graph for the 2D version of the movie:
