SM or LOTR...IMHO

Well you could sell me your TOTAN... Then you'd have room for two.

Kidding aside. That's a tough choice. Out of those 4 machines I would throw IM out of the equation immediately. Not in the same league as LOTR or SM and I imagine not on the same level as Tron (haven't played it yet so I can't say for sure). After that it depends what type of pin you prefer. LOTR is more of a shooter's game with a fantastic theme that blends perfectly with the gameplay. SM is more of a fast-paced game that plays very well and keeps you coming back for more. Personally, I give the edge to LOTR but mileage may vary. No matter what you're going to get a great pin!

They are both good just choose what theme would be in your interest

There are some machines with upgrades to game Roms but i dont think its
much of a difference though

Yes,that would have been nice to add.

Both games are great but I think SM would be a nice additon to your already sweeet collection.

i'd consider batman or spiderman. lots of modes and fast gameplay

I play IM and SM side by side in a public game-room. IM is not in the same league IMO. However, as it has been said here many times, you gotta go with what YOU feel as much as anything else. There are some people here that love a game that they own that I wouldn't play for free. Which of us is right? The answer is probably, BOTH! It's a very opinionated thing, the love of this game. Good luck to you either way. It looks like you should be happy with any of them since you're adding to such a fantastic collection....

Both great pins with a slight edge to SM.

I vote LOTR over SM. But honestly, what we all would choose is not important. If you can only afford one , and you can't decide.....you probably should wait until you are sure.