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

Optimization · Practiced Mastery
An easygoing co-op Kirby about recruiting enemies as friends and combining their elemental powers.

Optimization · Practiced Mastery
A deadpan janitor sim about mopping up the gory aftermath of sci-fi shooter battles.
Kirby Star Allies leans Optimization (Practiced Mastery); Viscera Cleanup Detail leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby Star Allies
Very low difficulty, AI allies carry fights
Viscera Cleanup Detail
Mop physics fumbling, lightly fiddly at most
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby Star Allies
Friend AI helps rather than opposes
Viscera Cleanup Detail
Nothing opposes you
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby Star Allies
Fixed layouts and bosses
Viscera Cleanup Detail
Messes are placed, not random in any meaningful way
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby Star Allies
Friend-ability element combos solve puzzles
Viscera Cleanup Detail
Efficient cleanup order and bucket logistics are the game
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.