I think the games are totally different. HoTD:Overkill is a pick-up-and-play game, something to play with your friends. It's very short, and the campiness is what makes it work. Extraction works on a whole different level. I like the cutscenes, as they remind you that you're a character in the story, not just a disembodied target. Besides, later in the game, you start seeing the game from different viewpoints, which is great.