i agree, like history have shown. Add-on won\'t sell that well. So, I doubt there will be any developers bother trying to make games in HD-DVD format for XBOX360 since it requires add-on HD-DVD drive in order to play, and consumers are more than likely won\'t bother going to spend the extra $200 just to play a game tin HD-DVD disc format.
So that\'s why built in are much more preferable. Plus, Blu Ray are better since it can hold more storage and more layers than HD-DVD. Don\'t forget both PS3 models ($500 and $600) have HDMI v1.3 ouput where XBOX360 lacks.