HD-DVD and blu-ray pictures are exactly the same, and often use the same video file on the disc. The big difference is that HD-DVD encryption has been cracked so it's now the consumer friendly format despite the wish of it's creators, while blu-ray is still the anti-consumer pro-studio format.
Having moved beyond plastic discs a couple of years ago, blu-ray with it's locked-in format is useless to me. HD-DVD can be copied to my media server and played at a click from a menu without the disc being present, and those files will be playable without restriction when HD-DVD and blu-ray are a distant memory.
Blu-ray has one advantage right now in that if you buy a PS3 and a $1,200 stereo, you can play uncompressed 7.1 audio over HDMI 1.3 rather than DTS-ES on several movies.