head to head
Resident Evil 0 asks more than Portal, and the gap is variance.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.

Optimization · Pure Optimization
Survival horror prequel built on swapping two characters with no item boxes.
Portal leans Optimization (Pure Optimization); Resident Evil 0 leans Optimization (Pure Optimization).
Portal leans a little harder on execution, though the gap is small.
Portal
Portal placement timing modest.
Resident Evil 0
Tank-control combat is modestly demanding
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
No adversary modeling player.
Resident Evil 0
Enemies follow fixed behaviour
Resident Evil 0 leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Resident Evil 0
Hidden layouts surprise until mapped
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Resident Evil 0
Two-character item juggling makes routing the real game
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.