I own both. LOTR wins for me.
TSPP has a crazier and deeper rule set, but LOTR has more long term "gotta play it" allure. Better flow, and more satisfying when you accomplish objectives, too.
TSPP is more approachable initially, but your guests will likely only play it a few times. LOTR has a better chance of locking them into a long-term love of the game.