head to head
Portal asks more than Outer Wilds, and the gap is execution.

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

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Outer Wilds leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Outer Wilds
Light piloting, mostly forgiving
Portal
Portal placement timing modest.
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
Portal
No adversary modeling player.
Outer Wilds leans a little harder on variance, though the gap is small.
Outer Wilds
Loop is deterministic once understood
Portal
Deterministic chambers; no randomness.
Outer Wilds leans a little harder on optimization, though the gap is small.
Outer Wilds
Pure knowledge puzzle - solve the system
Portal
Pure puzzle-solving optimization.
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.