two super different games - IM is fast and furious, loud (awesome) soundtrack, many modes, and interesting, fun shots.
TH starts off more leisurely, with several multiballs becomes SUPER fast and furious, includes an awesome soundtrack, WAY more modes than any other game, and some really satisfying shots in the form of the ramps. Most of the other shots require some precision to really nail. The game exhibits some next-level thinking with its use of the monster mechs. They will change your strategy and become permanent obstacles during certain modes. I've owned both, and only TH remains.