head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Skulls of the Shogun demands more reads.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.

Optimization · Pure Optimization
Tests turn-based positioning and resource play, sharpened by human opponents online.
Portal leans Optimization (Pure Optimization); Skulls of the Shogun leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Skulls of the Shogun
Turn-based orders need no dexterity
Skulls of the Shogun leans clearly harder on reads.
Portal
No adversary modeling player.
Skulls of the Shogun
Human multiplayer rewards anticipating opponent plans
Skulls of the Shogun leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Skulls of the Shogun
Little hidden beyond minor attack variance
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
Pure puzzle-solving optimization.
Skulls of the Shogun
Positioning, skull-eating economy and zone control are solvable
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.