I'd back HD against Blu Ray, cheaper, and like VHS over Betamax, it's the choice of the porn industry.
Blu-Ray is the better disc - faster and more data, its also backed by more film distributors - a major factor in sales, plus the PS3 is going to put a blu-ray player in millions of homes very early in the battle when most consumers havn't picked a player yet.
You'd also be betting against the royalty holder on the CDROM