Dominion is more 'Blattyesque'
I think Dominion is the better film inasmuch as it takes "the founder of our feast" - William Peter Blatty's - ideas seriously. It's much closer to Blatty's original novel, with its reflections of issues from that source, such as Merrin's pride and his tortured conscience. Two scenes stand out.
Where the younger priest confronts Merrin on his pride: would Merrin deny the comforts of faith to Che Che, just because faith no longer works for Merrin?
Where the nurse provokes Merrin into the statement, "I chose good. Evil happened."
In the same scene the nurse says, "I sometimes think the best view of God is from hell."
These scenes are suggestive of Blatty's themes - paradox, irony, the reality of evil expressed in just a few words.