head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Practiced Mastery
Twitch dodging and shooting layered over memorised arcade stage routes.

Execution · Pure Mechanics
A more combat-forward sequel with sharper platforming demands.
Metal Slug leans Execution (Practiced Mastery); Ori and the Will of the Wisps 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.
Metal Slug
Dodging dense bullet patterns and precise shots carry every credit
Ori and the Will of the Wisps
Combat plus escape chases demand tight inputs
Ori and the Will of the Wisps leans a little harder on reads, though the gap is small.
Metal Slug
Enemies follow fixed arcade scripts, never adapt
Ori and the Will of the Wisps
Scripted bosses, no human opponent
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug
Spawns are nearly deterministic once a stage is learned
Ori and the Will of the Wisps
Deterministic encounters
Metal Slug leans a little harder on optimization, though the gap is small.
Metal Slug
One-credit clears come from memorising routes and spawn patterns
Ori and the Will of the Wisps
Shard loadouts and weapon choice tune playstyle
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.