Hi-Def Digest has done one of the first head-to-head comparisons between Blu-ray and HD DVD using identical source material. The findings are pretty interesting.
Whatever its merits as a film, 'Training Day' has made history by becoming one of the first titles to be released on both the Blu-ray and HD DVD formats. In our first head-to-head comparison, we found the HD DVD to be superior. The unfortunate cropping of the Blu-ray image, coupled with more noticeable compression artifacts and an overall darker cast, can't compete with the more consistently pleasing presentation of the HD DVD.
If you'd like to read more, Hi-Def Digests comparison can be found here.