I have LOTR, STLE. and STTNG. First let me say that STLE plays like a completely different game than STTNG, despite the ramp layout similarity. So I wouldn't factor ownership of STTNG into the decision.
LOTR has a deeper ruleset right now but we know there will be some future code additions to STLE. So time will tell. If you can only have one or the other, I'd say go for STLE. Given the limited number of them, you'd probably be able to sell it for what it would cost to but a HOU LOTR in the future if you change your mind later.