Quoted from taylor34:

If you're going strickly on rulesets, TSPP is a much better game, not even that close. In LOTR, you can stack:
mode with a multiball
gollum with about everything
and that's essentially about it other than things like the 2x multiplier gift.
In TSPP you can stack:
mode on modes
multiballs on multiballs
several modes with several multiballs
2x multipliers, hurryups, victory laps, daredevils, treehouse of horrors, etc
basically everything.
LOTR is your traditional 'start mode and play it' type of game...TSPP is not. TSPP is all about stacking as much stuff as you can at once while keeping the clock going.
In LOTR, once you become good, every game basically becomes the same...qualify multiball, start and get 1/2 way, try and requalify. Over and over and over. The whole game becomes one big multiball after another attempting to beat it...becomes rather exhausting.
In TSPP, the games also become long. However, it's way less 'exhaustion' because every game is different...some games you might get several modes stacked, some games you might get to daredevil mania or springfield mystery spot, etc. There's just a lot more variety going on.
Basically, they're both good games, but TSPP has a much better long term ruleset.