I think the question presupposes that you need to invest in either right now. If you’re a gamer the choice might be made for you (HD with XBox, BR with PS3) but I still wouldn’t be buying many disks, unless they’re offering something amazing beyond the regular DVD and you’re not too uncomfortable with the idea of trading them in, should you be on the wrong train). I would hold off for the meantime. Later in 2008 it should be much clearer, though the answer might be “neither”.