Quoted from colonel_caverne:
X-Men: worth. All the more as the $ gap seems to be the weakest compared to other games. Playfield and software are différents
Acdc: not really worth. All the more as the mini playfield is quite useless. Drop target bank versus stand up target bank can't justify the price gap. Better light show as for all premium machines. but angus face is so ugly.
Tron: not worth. The biggest price gap as there is no premium pin. The eli ramp mod can tied LE machine. Drop target bank, recognizer moving and a MB added on the limited edition
Metallica: worth. hammer toy added, moving cross, disappearing ball lock into coffin, snake jaw
Star Trek: not worth. Amazing light show However on premium/LE
Walking Dead: worth. Light show, lifting ramp, crossbow
Kiss: not worth
Avengers:worth. hawk eye ramp and minor price gap with pro.
LOTR: not worth. esthetic improvements
Avatar: not worth. has a powerball starting 2x scoring
Rolling Stones: not worth. has a powerball starting 2x scoring
Elvis: not worth
What about Transformers, mustang, wrestlemania?
Star Trek Premium/LE also includes a kickback, webslinger, and crashing ship, in addition to the various light show improvements.