TWO DIFFERENT FILMS (PLEASE READ!!!)
Let me just start by saying I KNOW there are countless other threads about this topic, but you wouldn't believe how many dumbasses out there are still "confused." This movie (Dominion: Prequel to The Exorcist) is Paul Schrader's original film that was later remade by Renny Harlin. Renny Harlin's version is Exorcist: The Beginning. Dominion was filmed in 2002, but Morgan Creek rejected it and fired Paul Schrader because the movie "wasn't scary enough." They originally hired Renny Harlin to just reshoot a couple scenes, but they ended up having him reshoot the entire movie.
Exorcist: The Beginning came out in August 2004 and pretty much FLOPPED at the box office. Dominion was finally released on DVD in March 2005 after being shown at a film festival where it did very well. Being the Exorcist fan that I am, I own both movies on DVD (as well as the original, Exorcist II, and Exorcist III) and it is very nice to watch them both and compare. I don't think either of them suck, but Dominion is definitely a stronger film.
Most of the cast is the same in both films. The only major differences are:
-In Exorcist: The Beginning, the female doctor's name is Sarah Novak, and she's played by Izabella Scorupco
-In Dominion, the female doctor's name is Rachel Lesno, and she's played by Clara Bellar
-In Exorcist: The Beginning, Father Francis is played by James D'Arcy
-In Dominion, Father Francis is played by Gabriel Mann
-In Exorcist: The Beginning, Joseph (Remy Sweeney) is one of the main characters, but in Dominion, he and his brother James are played by different actors and neither of them is a main character
-The character of Cheche (Billy Crawford) only appears in Dominion. He kind of takes the place of Joseph in Exorcist: The Beginning (as being the fourth main character)