capacity & resilience
Thing with capacity is many Blu-Rays are released in 25GB format, and some in 50GB.
Almost all HD DVDs are 30GB, but can often be released on 2 discs if the equivalent Blu-Ray is a 50GB. That's 60GB total. Okay it's two discs, but lower costs and existing DVD replication plants means it's easy to do, and no one seems to care about 2 discs with DVDs these days.
As for resilience, I think Blu-Ray initially had some problem with the data layer being closer to the surface than on DVD, hence the scratch problem and resolving it with a coating. I got the impression it was less of an issue on HD DVD.
The best thing now is for Sony to do what they should have a couple of years back and take up the offer to join with HD DVD. Create a dual-format or merge the standards under one name, then have dual-format players, and release whatever format they like for a title and then anyone with a dual-player can play them without a care in the world. Like with DVD+/- R formats.
Early adopters and PS3 owners will have to buy players for the alternate format though, unless dual-format discs are released.