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 · Pure Mechanics
A run-and-gun boss rush about dodging scripted patterns with tight inputs.

Execution · Pure Mechanics
Tests frame-tight jump timing through fully memorisable obstacle sequences.
Cuphead leans Execution (Pure Mechanics); The Impossible Game leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Cuphead
Tight dodging and parry timing decide every boss.
The Impossible Game
One mistimed jump restarts the level - perfect inputs win alone
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Cuphead
Bosses cycle scripted phases; no adaptation to player.
The Impossible Game
Solo - nothing to predict
Cuphead leans a little harder on variance, though the gap is small.
Cuphead
Minor attack-order shuffling between phases.
The Impossible Game
Levels are identical on every attempt
Cuphead leans a little harder on optimization, though the gap is small.
Cuphead
Loadouts and boss phase order are fully learnable.
The Impossible Game
Memorising the jump sequence is half the climb
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.