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

Execution · Practiced Mastery
A linear, cinematic Metroid mixing third-person action with first-person aiming.

Execution · Practiced Mastery
Modern 2D Mario platformer built on classic jump precision and hidden exits.
Metroid: Other M leans Execution (Practiced Mastery); New Super Mario Bros. leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid: Other M
Dodge-timing and pointer-switch finishers
New Super Mario Bros.
Jump timing and momentum control carry every level
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid: Other M
Bosses run scripted patterns
New Super Mario Bros.
Enemies follow fixed scripted patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid: Other M
Linear, deterministic encounters
New Super Mario Bros.
Levels fully deterministic once seen
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid: Other M
Learning boss movesets and item routes
New Super Mario Bros.
Secret exits, star coins, and route 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.