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

Optimization · Pure Optimization
JRPG where you program party AI through its gambit system.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Final Fantasy XII leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Final Fantasy XII
Gambits automate combat away from the hands
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.
Final Fantasy XII
Enemy AI is fixed and exploitable
Portal
No adversary modeling player.
Final Fantasy XII leans clearly harder on variance.
Final Fantasy XII
Rare spawns and drop RNG
Portal
Deterministic chambers; no randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Final Fantasy XII
Programming gambit logic IS the gameplay
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.