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.

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

Optimization · Practiced Mastery
Dimension-hopping spectacle platformer built on the classic arsenal-upgrade loop.
Limbo leans Execution (Practiced Mastery); Ratchet & Clank: Rift Apart leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Limbo
Tight platforming with trial-and-error.
Ratchet & Clank: Rift Apart
Dodging, rift-tether mobility, and weapon aim.
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.
Ratchet & Clank: Rift Apart
Scripted enemies and setpieces only.
Ratchet & Clank: Rift Apart leans a little harder on variance, though the gap is small.
Limbo
No randomness.
Ratchet & Clank: Rift Apart
Unknown encounters on first run.
Ratchet & Clank: Rift Apart leans a little harder on optimization, though the gap is small.
Limbo
Puzzles have fixed solutions.
Ratchet & Clank: Rift Apart
Weapon leveling and bolt economy reward planned play.
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.