I'm not sure if I would call it different endings, but the end can vary based on your decisions and actions. In particular regarding the

a) Showdown: If you have informed the mafia of Mickey's cooking the books, he will not be in the showdown at the docks, which makes the showdown a bit easier.
b) End scene: Depending on your actions you can leave with or without Joe.

Do you mean Dale when you arrive in Christines apartment for the first time? This decision is one of several decisions impacting the relationship between Christine and Joe, which determines the end scene.