Here are a few things to consider since you are the one that will own the pinball.
1. Do you like AFM or Tron better.
2. Is the price fair for the condition of AFM that you are looking at.
3. The AFM will be a better investment (if bought right) then the Tron.
4. If you don't like AFM after owning it for awhile, then you can easily sell it for what you paid for it.
5. drawback is MM, AFM and LOTR all play very similar. Your themes are different but layout and shots are similar.
I say don't let others make up your mind. Buy what you want. After all you are the one that will be playing it.
Good luck