head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Warlock: Master of the Arcane demands more variance.

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

Optimization · Pure Optimization
Specializing magical cities and unlocking spells to dominate a randomly generated arcane world.
Portal leans Optimization (Pure Optimization); Warlock: Master of the Arcane leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Warlock: Master of the Arcane
Fully turn-based hex strategy; no physical precision ceiling
Warlock: Master of the Arcane leans clearly harder on reads.
Portal
No adversary modeling player.
Warlock: Master of the Arcane
AI lords use scripted expand-and-attack patterns without real modelling
Warlock: Master of the Arcane leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Warlock: Master of the Arcane
Random spell research results and dungeon encounters add genuine unknowns
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.
Warlock: Master of the Arcane
City specialization and spell unlocking form the dominant solvable layer
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.