I never want to play a 15 or 20 minute game of pinball. Seriously, all my games get set up crazy nasty because of that.
Having said that, I vote for IM all day every day. The game is straight up nasty. Every shot can be hit safely, and every shot can be a drain if you don't hit it just right. For everyone who says that IM is so random, I argue strongly that it isn't - it's just that if you hit even a hair off, you are in trouble.