Man this is a tough one, mainly because it's pitting one of my favourite series against one of my favourite horror movies.
I think I'm swaying slightly towards Event Horizon - for the main reason that we seem to be focusing on "evil Dr Grant" (lol), ie Dr Weir as the threat, but remember he was an innocent person who was turned evil by the ship. He's not the enemy, the ship is.
The ship corrupts and turns people evil and crazy, breaking their will through visions, fear and horror.
This is something Hannibal, a brilliant psycho, almost managed to do to Will over a sustained and long period. I see Event Horizon as being able to inflict a more horrible and compressed version of what Hannibal tried to achieve.
Will did nearly go crazy, and started making some very questionable choices under the relatively gentle but consistent pressure Hannibal applied. I reckon Event Horizon will be like applying a hammer to that same fragile psyche and Will will become the new reigning lord of the spaceships hell.