head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Practiced Mastery
A monochrome puzzle-platformer about a boy lost in limbo.

Optimization · Practiced Mastery
Tests patience with scripted encounters and light adventure-game routing.
Limbo leans Execution (Practiced Mastery); The Lord of the Rings: The Fellowship of the Ring leans Optimization (Practiced Mastery).
Limbo leans a little harder on execution, though the gap is small.
Limbo
Tight platforming with trial-and-error.
The Lord of the Rings: The Fellowship of the Ring
Basic melee, archery and stealth need only modest timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Limbo
Hazards are scripted.
The Lord of the Rings: The Fellowship of the Ring
Enemies follow simple scripts; nothing adapts
The Lord of the Rings: The Fellowship of the Ring leans a little harder on variance, though the gap is small.
Limbo
No randomness.
The Lord of the Rings: The Fellowship of the Ring
Encounters are fixed; little is random once seen
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Limbo
Puzzles have fixed solutions.
The Lord of the Rings: The Fellowship of the Ring
Learning levels, item use and encounter order carries the game
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.