Well there's a few different theories.
One (and this is the one I subscribe too) is the money thing. There are laws in Canada that if you cast a Canadian in one of the two lead roles of your film than the Canadian government will pay large amounts of your budget for you, as well as give you deals on location costs. This is partly why EVERY frigging movie is being shot in Canada now adays. So by not hiring Hodder, and hiring Kirzinger (a native Canuck) the production is entitled to that money.
The "poetic eyes" thing (a studio rumor, and I think complete bullshit) this was an early rumor, saying that the film was going for a sort of "phantom of the opera" type thing with Jason and they wanted somebody with "sad, expressive eyes" and they said Hodder just didn't have that. Complete shit.
The "closer to size" theory. Also obviously bullshit considering that Kirzinger is taller and they have him in platform shoes. Yu himself has said that he always thought of Jason as "larger than life" so he claims he wanted someone bigger than Kane (although, the height difference is minimal and could have easily been made up with riser shoes).
Finally, I recently interviewed Jason X screenwriter Todd Farmer for my website, and I got him talking about the subject, he was very pissed off and said he feels that it was their way of separating themselves from the previous 'Friday the 13th' sequels. Just a theory, but the way he presents it sounds credible.
And for the record...I am very much looking forward to this flick, mainly because in my early horror loving days I was weaned on 80's slashers.
And Jason will kick Freddy's ass.
