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

Optimization · Pure Optimization
Coordinating three characters through fixed object-logic puzzles.

Optimization · Systems & Chaos
Puzzle adventure about coaxing a giant half-tame creature through ancient ruins.
The Cave leans Optimization (Pure Optimization); The Last Guardian leans Optimization (Systems & Chaos).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
The Cave
Undemanding platforming with no timing pressure
The Last Guardian
Slow climbing and platforming, very forgiving
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
The Cave
No adversary - a narrating cave is not a mind
The Last Guardian
Trico is willful but not modeling you adversarially
The Last Guardian leans a little harder on variance, though the gap is small.
The Cave
Each character's section is unknown on first descent
The Last Guardian
Trico's unpredictable compliance adds noise
The Cave leans a little harder on optimization, though the gap is small.
The Cave
Three-character object-shuffling puzzles are the whole game
The Last Guardian
Environmental puzzles with intended solutions
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.