head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; World of Final Fantasy demands more variance.

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

Optimization · Pure Optimization
A chibi Final Fantasy spin-off about capturing monsters and stacking them into totem teams.
Portal leans Optimization (Pure Optimization); World of Final Fantasy leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
World of Final Fantasy
Turn-based stacking combat; no dexterity
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.
World of Final Fantasy
Scripted bosses with fixed gimmicks
World of Final Fantasy leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
World of Final Fantasy
Mirage capture conditions hidden until learned
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
World of Final Fantasy
Stack composition and mirage boards are a solvable system
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.