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

Optimization · Pure Optimization
A knowledge-based mystery solved by mapping a deterministic solar system.

Optimization · Pure Optimization
A hardcore programming-in-disguise puzzle where you wire atomic assembly lines to synthesize compounds.
Outer Wilds leans Optimization (Pure Optimization); SpaceChem leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Outer Wilds
Light piloting, mostly forgiving
SpaceChem
Drawing waldo paths requires no physical precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Outer Wilds
World is fixed; nothing adapts to you
SpaceChem
No opponent; pure logic construction
Outer Wilds leans a little harder on variance, though the gap is small.
Outer Wilds
Loop is deterministic once understood
SpaceChem
All reactor inputs are deterministic and fixed
SpaceChem leans a little harder on optimization, though the gap is small.
Outer Wilds
Pure knowledge puzzle - solve the system
SpaceChem
Designing correct chemical pipelines that transform inputs to outputs exactly
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.