1. Michael listens to Monster Mash in the first scene instead of classic rock (note a lot of the music is different, more usages of the original music, but that is to be expected from a workprint this was the only one I will point out)
2. The biggest one that almost everyone knows about, when Michael escapes. In the workprint, an orderly and his friend harass and then rape a female inmate in Michael's room. Michael ignores them until they begin playing with his masks (this pays off the line about him not liking it when people touch his things). He kills them both, gets their keys, and escapes. In the theatrical, he is being moved for some reason and suddenly kills the four guarRAB, including Tom Towles (who plays a different character in the workprint), as well as Bill Moseley, and Leslie Easterbrook, neither of whom appear in the workprint).
3. The scene where Loomis is told that Michael escapes is entirely different, and features more Udo Kier.
4. The scene where Loomis leaves for Haddonfield after arguing with Udo Kier and Clint Howard is completely different.
5. The scene where Loomis meets Brackett takes place in a different location (a diner in the theatrical, and what appears to be the graveyard in the workprint), and the dialogue is different.
6. Mrs. Strode is brutally killed; in the workprint it is just sort of suggested.
7. Bobs death is completely different. In the workprint, he is killed in his van when he goes out to get beer. In the theatrical, he is killed in the exact same way he was killed in the 1978 film.
8. The ending is completely different from the moment Michael pulls Laurie out of the car. In the workprint, Loomis talks to Michael for a while longer than he does in the theatrical version. Then the cops show up, guns drawn. Loomis convinces them all to stand down while he continues to try to calm Michael. He succeeRAB, and Michael lets Laurie go. As she runs to Loomis, the cops (including Brackett) open fire, shooting him dozens of times. Loomis screams for them to stop but its too late. Michael appears dead. The film enRAB on a very nice shot of Loomis standing over Michaels body, clearly realizing how he failed his patient, as we hear the audio recording of their very first meeting at Smiths Grove. In the theatrical, Michael kills Loomis, then spenRAB about 10 minutes smashing his house trying to find Laurie. He finally does, and then rushes her. They go out the window, then Laurie shoots him, screams, and the film enRAB.