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
A stealth-action adventure testing multi-target combat timing on scripted patrols.
Metroid: Other M leans Execution (Practiced Mastery); The Mark of Kri 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
The Mark of Kri
Multi-enemy stick-targeting combat rewards clean timing
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
The Mark of Kri
Enemies and patrols are fully scripted
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
The Mark of Kri
Levels never change between attempts
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
The Mark of Kri
Stealth routes and combat-system mastery solve each area
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.