Is there any quality difference between blue-ray and hd-dvd?
No, there isn't. Not even in capacity anymore. 1080p is 1080p is 1080p no matter how you dress it up. Regardless of blu ray, black ray, plaid ray, HD dvd, Super HD dvd, or quantum scientific notation HD DVD.
HD DVD has already been scaled to meet the same capacity rates as blue ray, the problem is its not public yet or produced yet because of patent filing most likely.
Speaking of IP (intellectual property) law, sony is being sued right now for a violation with the blu ray technology. So, lets see how that pans out.
The problem is, with most technology, products like this are blogged and reported wrong. Information is skewed, construed, and distorted to favor one of the other. Really when it comes to consumer products more misinformation is given than actual facts. Which is why I am starting to really hate magazines, professional bloggers, Tomshardware.com (which is a shame), sales reps, and even consumer reports. There is no physical quality difference between blu ray or HD DVD they display the exact same HD resolutions.
I personally do not like either of them, they are allowing developers and media companies to become sloppy now. DVD 14 and DVD 18 which is what we currently use (the predecessor of DVD 9) holds up to 15 gigs uncompressed. Seriously what movie and/or game needs 15 gigs of data. Crysis that DX10 game that is going to blow everything out of the water requires 6 gigs of HD space. Gaming doesn't need that much and developers that are saying its only possible on blu ray are full of crap, and are probably being paid or get kick backs from sony for saying so. This also allows them to ignore compression technology which also gets better and better every year.
Blu ray also said, no adult movie industry you can't use our technology. Adult movie industry said suck it, we are using HD DVD anyways. Last I read from wired magazine the porno industry releases an average of 11,000 DVD movies a year. It is a profitable market, and people apparently like their porn.
In all honesty there is no difference, no matter who tells you different. No one will know what will happen in the future, but my personal guess is they will both live. This reminds me of the DVD + and the DVD - format wars and how everyone was like, oh no! Two DVDs enter 1 DVD leaves, yet I still see both formats all over the place and every DVDRW drive you buy now reads/writes both formats. I am sure that HD/blu-ray will end up the same way.