HD-DVD lost the format war against BD, just due to less space storage. Despite both are suitable for different purposes.
Because I am typing on a mobile device, and my clipboard (limited to twenty items) is full, I will just describe it here.
The main disadvantage of BluRay is the same as in CD, just on the other side: the (horrible) position of the data layer.
I know, being just 100ųm away from the surface makes BD more accurate for reading and writing data, but really fragile. Resurfacing is effectively not possible.
The data surface of DVD and HD-DVD is exactly in the middle, 600 ųm away from each surface side. So it requires much deeper scratches from either side in order to cause serious damage.
Additionally, there is no BD-RAM, but HD-DVD-RAM, and even HD-DVD-RAM DL.
Mass production of media (e.g. for large software) costs even less than BD LTH (low-to-high. More information on Wikipedia.).
I am not claiming, that HD-DVD is superior, but rather intended for price worthy data archival.
Hopefully, mankind will bring us the next ultimate optical storage revolution, HVD, pretty soon.
Data should be redundantly mirrored on at least two more positions on the disc to avoid loss of information with damage.
In my opinion, both should exist. BD and HD-DVD.
Also CD-RW×32, DVD-RW×6 and DVD-RAM in higher speed classes (see Wikipedia) should be available.