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

Execution · Pure Mechanics
Brutal one-hit-death shmup execution over patterns that must be memorised to survive.
Cuphead leans Execution (Pure Mechanics); Silver Surfer 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.
Silver Surfer
One-hit deaths demand near-perfect dodging every second
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.
Silver Surfer
Enemy waves are fully scripted patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Cuphead
Minor attack-order shuffling between phases.
Silver Surfer
Stages replay identically once learned
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Cuphead
Loadouts and boss phase order are fully learnable.
Silver Surfer
Memorising spawn patterns and safe lines is mandatory study
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.