head to head
Neither is simply harder - they are hard in different places. Fire Emblem: Awakening demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Engineering unit pairings and reclass paths to dominate maps whose enemy scripts are fully mappable.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Fire Emblem: Awakening leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Fire Emblem: Awakening
No twitch elements; pair-up placement is the only spatial decision under time
Portal
Portal placement timing modest.
Fire Emblem: Awakening leans a little harder on reads, though the gap is small.
Fire Emblem: Awakening
Enemies follow simple aggro patterns on fixed maps
Portal
No adversary modeling player.
Fire Emblem: Awakening leans clearly harder on variance.
Fire Emblem: Awakening
Hit and crit rates plus random level-up stats create run variance
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.
Fire Emblem: Awakening
Marriage pairings and Second Seal reclass chains are the optimization spine
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.