Toshiba had talked about a triple layer 45GB disc back in May 2005, but by pushing capacity to 51GB the company may aim to get it out while Blu-ray dual-layer discs offer 50GB capacity. Of course, Blu-ray is not "stuck" at 50GB just as Toshiba is not stuck with 30GB, and a Blu-ray disc with 4 layers offers an impressive 100GB capacity. For now though, even HD DVD's 30GB capacity has been adequate for high-definition movie releases.
HD DVD's 3X DVD has also achieved considerable media attention lately considering the possibilities it offers; providing high-definition (720p) movies on a (DVD) disc that is cheap to produce and works with all HD DVD hardware. Blu-ray supporters can also be happy with the format outselling HD DVD since the PS3 launch. Right now though, both sides still have some price reductions to consider to open HD to a larger market.
Source:
HDTV News