Sony developed Blu-ray along with some other companies because the royalties from DVD were going to dry up at some point, and they needed a new revenue stream. Putting high definition onto regular DVDs with a red laser could be done, but at the sacrifice of special features and some small sacrifice in quality. Blu-ray needed a full 50GB of capacity because the original plans were to use MPEG-2, the same encoding format used for DVDs.
Toshiba developed a less expensive version of a blue laser disc using the same physical structure as regular DVDs, and they planned to use MPEG-4 or other, more efficient encoding than MPEG-2; so they could get away with 30GB of capacity and produce the same quality as Blu-ray at 50GB.
I think he meant why are some blue-ray exclusive movie available on HD-DVD internationally. This is because some studios like warner are blue-ray exclusive only in the us.
Blu-ray has more capacity because it uses near-field recording, but that does not make it "better." It is harder and more expensive to manufacture, requires a special hard coat and lenses with high numerical aperture. Production yield is abysmal for the discs. The BD-Java encoding is difficult, and the copy protections may prevent users from delivering the content from their own home servers, a problem that caused HP to switch support to HD DVD. It is anti-consumer, and that is one reason it won the support of 20th Century Fox and Disney. I don't see anything about it that is superior to HD DVD except its capacity, something no longer really needed once Sony realized it did not need MPEG-2 encoding.
