2D/3D - same disc question

[Chrisco84]

Hi guys.
I'm new to 3D and I have a quick question.
Does either the 2D or 3D quality of a movie suffer if they are on the same blu-ray disc?
For example: I want to get Men in Black 3 3D. It comes in a single disc set with both 2D and 3D versions on the same disc or a Quad pack where the 2D and 3D versions are on seperate discs.
Would the quad pack be superior because they are spread over 2 discs or is having both 2D and 3D on the same disc exactly the same quality?

[Anamnesis]

Generally the 2D version suffers as a result of the 3D down conversion (ie. you are only seeing 1 of the 2 images and thus it may not reflect the quality of an encoded done specifically for the 2D), however I have not personally seen any 2D Version that also had a 3D disc so I can only go by what the whitepapers say.

[cyrax83]

As far as I know, the 3D movies only show an offset of the 2D image, i.e. it only stores the difference from 2D version to generate the 3D image - so the 2D version should be the same.

I may be wrong

[Sky_Captain]

The 2D version is extracted from one of the eye streams. Whatever issues come from this, space isn't one of them, as there's not two transfers crammed onto the one disc, despite what some people might think.