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

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

Execution · Practiced Mastery
The famously punishing Japanese sequel to Super Mario Bros., built for players who mastered the original.
Cuphead leans Execution (Pure Mechanics); Super Mario Bros.: The Lost Levels leans Execution (Practiced Mastery).
Cuphead leans a little harder on execution, though the gap is small.
Cuphead
Tight dodging and parry timing decide every boss.
Super Mario Bros.: The Lost Levels
Brutal precision jumps, poison mushrooms punish any input slip
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.
Super Mario Bros.: The Lost Levels
No adaptive opponent; everything is scripted
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.
Super Mario Bros.: The Lost Levels
Hidden blocks and warp zones until memorised
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.
Super Mario Bros.: The Lost Levels
Level memorisation and warp routing are half the battle
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.