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
Retro Studios' notoriously tough revival of Donkey Kong Country with relentless set-piece levels.

Execution · Pure Mechanics
Rhythm FPS where every shot must land on the metal soundtrack's beat.
Donkey Kong Country Returns leans Execution (Pure Mechanics); Metal: Hellsinger 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.
Donkey Kong Country Returns
Demanding rocket-barrel and mine-cart sections, strict timing
Metal: Hellsinger
shooting on the beat is the entire skill test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Donkey Kong Country Returns
Scripted hazards, no adaptation
Metal: Hellsinger
demons follow fixed behavior
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Donkey Kong Country Returns
Hidden puzzle pieces, fixed once found
Metal: Hellsinger
deterministic arenas
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Donkey Kong Country Returns
KONG letters and time attack routes are learnable
Metal: Hellsinger
weapon choice and streak management for scores
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.