I owned IM and have a Tron LE. I personally think that Tron is a better game. IM got stale after about 6 months. Monger is cool, War Machine is cool but the wizard mode (spinner countdown) is terrible and I wasn't a big fan of the Whiplash Multiball. I hate the up the middle spinner shot for a wizard mode. It just seems so cheap and there should have been a deeper wizard mode made IMHO. Jericho mini wizard mode is cool but is too easy to get too. IM again IMHO could have been a top ten game if it wasn't in the downsizing time at Stern. I really hope Avengers (if it's made) will blow it out of the water. I also think that IM was a really easy game. Once you know how to shot Iron Monger without the ball touching the magnet it's an easy mode. It's a good game just not great.
Tron is a deeper game. I like the add a ball feature on Quorra Multiball. That damn GEM shot is a tough one. Spinning Disc is a great complement to the game. Ramps are nice and it's nice to have a game made by Stern again that has 3 flippers. The LE lighted ramps are amazing.