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

Optimization · Pure Optimization
Stacking tome and trait combinations across procedurally generated worlds with faction-wide consequences.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Age of Wonders 4 leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Age of Wonders 4
All decisions are turn-based; nothing physical
Portal
Portal placement timing modest.
Age of Wonders 4 leans clearly harder on reads.
Age of Wonders 4
AI rulers use scripted tomes and no real player modelling
Portal
No adversary modeling player.
Age of Wonders 4 leans clearly harder on variance.
Age of Wonders 4
Procedural world generation and tome discovery add hidden layers
Portal
Deterministic chambers; no randomness.
Age of Wonders 4 leans a little harder on optimization, though the gap is small.
Age of Wonders 4
Tome selection and trait stacking create a vast combinatorial optimization space
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.