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 relaxed co-op collect-a-thon testing little beyond completionist routing.
Kirby Star Allies leans Optimization (Practiced Mastery); LEGO Pirates of the Caribbean: The Video Game 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
LEGO Pirates of the Caribbean: The Video Game
Forgiving brawling and platforming for all ages
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
LEGO Pirates of the Caribbean: The Video Game
Enemies are harmless scripted props
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
LEGO Pirates of the Caribbean: The Video Game
Collectible locations are fixed, just initially unknown
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
LEGO Pirates of the Caribbean: The Video Game
Completionist collectible routing is the only real puzzle
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.