head to head
Neither is simply harder - they are hard in different places. Front Mission 4 demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Tactical mecha RPG where customizing wanzer parts and link systems outweighs battlefield improvisation.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Front Mission 4 leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Front Mission 4
Menu-driven turn-based combat
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.
Front Mission 4
Fixed mission AI with set behaviors
Portal
No adversary modeling player.
Front Mission 4 leans clearly harder on variance.
Front Mission 4
Accuracy rolls and link-attack triggers
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.
Front Mission 4
Wanzer part builds and pilot skill loadouts are the game
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.