How can the 25GB King Kong HD Port be considered "reference material"?

[blu-ballz]

I see there are two versions of the film and no extras on the 50GB BD. I don't have a BluRay computer drive so am assuming there are actually two slightly different copies of the movie, possibly 3 with the PiP version?

Does someone have a filesize breakdown?

Now to my point, if I am correct in stating we are actually watching the same Video Image as was on the HD-DVD, how at around 20GB can it be considered better video quality than a full blown 50GB movie like so many others out there? Is there really no difference what the human eye can visuallize whether a 25GB file or what you would think should be two times better at 50GB?