First off, I should say that I am format neutral and don't want to start a flame war. An interesting question that I would like to hear answered by with experience in both formats what their preference is, and why. If you don't own both, please refrain from posting.
I just recently picked up my HD DVD player and I think I am personally becoming partial to that format. I love the way they set up their menu system, and how they decided to do the commentaries I think is an awesome feature as well. It offers some actual functional difference in playback over Blu-ray, which now that I have used HD DVD seems to be another iteration of DVD, the only difference being improved quality.
I just recently picked up my HD DVD player and I think I am personally becoming partial to that format. I love the way they set up their menu system, and how they decided to do the commentaries I think is an awesome feature as well. It offers some actual functional difference in playback over Blu-ray, which now that I have used HD DVD seems to be another iteration of DVD, the only difference being improved quality.

















If you can't take the heat, get out of the kitchen!
Yes there is a PQ difference, get your system calibrated.

