head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Pure Mechanics
Memorising brutal scripted patterns and executing them without a single slip.

Execution · Pure Mechanics
A run-and-gun boss rush about dodging scripted patterns with tight inputs.
Contra: Hard Corps leans Execution (Pure Mechanics); Cuphead 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.
Contra: Hard Corps
One-hit deaths under relentless bullet pressure demand perfect inputs
Cuphead
Tight dodging and parry timing decide every boss.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Contra: Hard Corps
Bosses are fully scripted setpieces
Cuphead
Bosses cycle scripted phases; no adaptation to player.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Contra: Hard Corps
Everything fixed once routes and patterns are known
Cuphead
Minor attack-order shuffling between phases.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Contra: Hard Corps
Memorising boss patterns, weapons and branching routes is mandatory
Cuphead
Loadouts and boss phase order are fully learnable.
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.