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

Optimization · Pure Optimization
Maximizing Emblem synergies and inherited skills to dismantle precisely scripted enemy maps.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Fire Emblem Engage leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Fire Emblem Engage
Turn-based; Engage ring timing is menu-driven not reactive
Portal
Portal placement timing modest.
Fire Emblem Engage leans a little harder on reads, though the gap is small.
Fire Emblem Engage
Scripted enemy phases never adapt to player tendencies
Portal
No adversary modeling player.
Fire Emblem Engage leans clearly harder on variance.
Fire Emblem Engage
Hit and avoid stats tighten variance; Engage mechanics are reliable
Portal
Deterministic chambers; no randomness.
Fire Emblem Engage leans a little harder on optimization, though the gap is small.
Fire Emblem Engage
Emblem pairing, skill inheritance, and unit positioning are exhaustively solvable
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.