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
The 3DS remake of Metroid II built around a precisely timed melee counter.

Optimization · Practiced Mastery
A minimalist action adventure about toppling sixteen colossal puzzle-bosses.
Metroid: Samus Returns leans Execution (Practiced Mastery); Shadow of the Colossus 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.
Metroid: Samus Returns
Melee-counter timing defines nearly every fight.
Shadow of the Colossus
Climbing, grip management, and sword timing on moving giants.
Shadow of the Colossus leans a little harder on reads, though the gap is small.
Metroid: Samus Returns
Counters punish scripted lunges, not adaptation.
Shadow of the Colossus
Colossi follow fixed behavior patterns.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metroid: Samus Returns
Fixed map and encounters.
Shadow of the Colossus
Encounters play out nearly identically each attempt.
Shadow of the Colossus leans a little harder on optimization, though the gap is small.
Metroid: Samus Returns
Aeion management and ability routing matter.
Shadow of the Colossus
Each colossus is a solvable climbing 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.