Well, as far as HD DVD vs. Blu-ray goes, it looks like we've pretty much passed the point of no return now; with each passing day it seems less and less likely that a compromise will be reached on a next-gen format. The ongoing peace talks between the two camps, which have been on-again, off-again for months now, seem to have finally dissolved. It's disappointing, but however you feel about the fact that the HD DVD and Blu-ray factions squandered countless chances to make it right and come together, it looks like in just a few short months they're going to be duking it out mano a mano right in our livingrooms. There may not be a lot we can do to fight back - apart from refusing to adopt either format out of sheer spite of their pigheadedness - but no matter what we might as well at least arm ourselves with the knowledge necessary to understand the nature of the situation at hand.
Here's the background:
Philips's development of the Laserdisc in 1969 yielded many of the technologies Sony carried over and adopted when they partnered with Philips to create a little something called the CD way back in '79. Both companies were hard at work together once again in the early 1990s on a new high-density disc called the MultiMedia Compact Disc (MMCD-original name, guys), but their format was eventually more or less abandoned in favor of Toshiba's competing Super Density Disc (SD), which had the vast majority of backers at the time, such as Hitachi, Matsushita (Panasonic), Mitsubishi, Pioneer, Thomson, and Time Warner.
The two factions cut a deal, brokered by IBM president Lou Gerstner, on a new format: DVD. Toshiba wound up on top after the dust settled in 1995/1996, and Sony and Philips, who weren't cut in on the standard (and royalties) nearly as much as they'd have liked, immediately started work on a next gen system. The Professional Disc for DATA (aka PDD or ProDATA), which was based on an optical disc system Sony had already been developing in the side, would eventually become the Blu-ray disc. Toshiba, not to be outdone by the pair, also started work on a next gen system, the Advanced Optical Disc, which eventually evolved into the HD DVD. After thirty-five years of optical audio/video disc development we're back where we were years ago: two money-grubbing factions fighting each other and threatening to wreak havoc on the consumer electronics industry. Apparently history really does repeat itself.
So here's the technical nitty gritty before we drop the graphs n' charts on ya. Both systems use the same kind of 405nm wavelength blue-violet laser, but their optics differ in two ways. Since the Blu-ray disc has a tighter track pitch (the single thread of data that spirals from the inside of the disc all the way out—think grooves on a 12-inch vinyl single vs. an Elvis Costello full-length album), it can hold more pits (those microscopic 0s and 1s) on the same size disc as HD DVD even with a laser of the same wavelength.
The differing track pitch of the Blu-ray disc makes its pickup apertures differ, however—0.65 for HD DVD vs. 0.85 for Blu-ray—thus also making the two pickups technically incompatible despite using lasers of the same type. HD DVD discs also have a different surface layer (the clear plastic layer on the surface of the data—what you get fingerprints and scratches on) from Blu-ray discs. HD DVD use a 0.6 mm-thick surface layer, the same as DVD, while Blu-ray has a much smaller 0.1mm layer to help enable the laser to focus with that 0.85 aperture.
Herein lies the issues associated with the higher cost of Blu-ray discs. This thinner surface layer is what makes the discs cost more; because Blu-ray discs do not share the same surface layer thickness of DVDs, costly production facilities must be modified or replaced in order to produce the discs. A special hard coating must also be applied to Blu-ray discs, so their surface is sufficiently resilient enough to protect the data a mere 0.1mm beneath—this also drives the cost up. The added benefit of keeping the data layer closer to the surface, however, is more room for extra layers.
Still with us? No? Blu-ray discs are more expensive, but hold more data—there, that's all.
Other interesting facts:
The Nichi Corporation, who holds the design patents to the Blu-ray's laser system, sits as an associate member of the HD DVD Promotion Group.
Even though Apple sits on the Blu-ray Board of Directors, its DVD Studio Pro software supports authoring HD DVD media.
Blu-ray, unlike HD DVD, requires a hard coating on its discs because it's 0.5m closer to the surface. The polymer coating it uses, called Durabis, was developed by TDK and is supposedly extremely resilient and fingerprint resistant.
The Java platform is mandatory on Blu-ray as it's the standard for menus/multimedia (i.e. all Blu-ray systems must support JVM)
Though Microsoft has not officially sided with either format, it has a number of long-standing IP cross-licensing deals with Toshiba. HD DVD systems will run Windows CE; the standard is currently the only next-gen optical standard with announced support in Longhorn, and an HD DVD version of the Xbox 360 is rumored for the future.
The first consumer Blu-ray device in the US market is expected to be the PlayStation 3.