This isn't meant to troll.
Sure they're the same demo, but let's see the pros and cons of both of them. Starting with PS3,as I am playing the demo at this very moment, starting with Leon. Here's some of the pros, I see no screen tearing anywhere so far in the PS3 demo, which is amazing the games feels smooth,while on the xbox it felt weird. As for the character models, they look better as well on the PS3. The reason for screen tearing is that the xbox has to suffer with two discs .. Moving onto the cons of the PS3 version,I can't seem to find any at the moment..Everything feels too good.
Now onto the Xbox version, I gotta say I really find the xbox version to be a bit ugly, starting with the cons, I really don't like the controls I guess it's cause I'm not use to RE on the xbox. And cause the game is on two discs, I wish xbox had one disc. Now the moment you've been waiting for the pros... I love has fast paced it is.
Now for my final comment, I gotta give the edge to the PS3, due to it's hardware and one disk and no screen tearing.