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.

Optimization · Pure Optimization
Sequel that adds a mother-daughter pair to its impossible-architecture puzzles.

Optimization · Pure Optimization
Coordinating three characters through fixed object-logic puzzles.
Monument Valley 2 leans Optimization (Pure Optimization); The Cave leans Optimization (Pure Optimization).
The Cave leans a little harder on execution, though the gap is small.
Monument Valley 2
Gentle touch controls, no reflexes
The Cave
Undemanding platforming with no timing pressure
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Monument Valley 2
Nothing opposes you
The Cave
No adversary - a narrating cave is not a mind
The Cave leans a little harder on variance, though the gap is small.
Monument Valley 2
Deterministic authored levels
The Cave
Each character's section is unknown on first descent
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Monument Valley 2
Geometry manipulation puzzles with intended solutions
The Cave
Three-character object-shuffling puzzles are the whole 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.