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 classic 2D Mario platformer rewarding tight jump execution above all.

Execution · Pure Mechanics
A classic Contra-style run-and-gun about precise reflexes and firepower.
New Super Mario Bros. U Deluxe leans Execution (Pure Mechanics); Operation C 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.
New Super Mario Bros. U Deluxe
precise jump and platforming execution
Operation C
precise run-and-gun reflexes and dodging
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U Deluxe
fixed enemy patterns, no adaptation
Operation C
scripted enemy patterns, no adaptation
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U Deluxe
minor enemy placement randomness
Operation C
minimal randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U Deluxe
level routing for speed/collectibles
Operation C
weapon pickup routing knowledge
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.