head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; The Escapists: The Walking Dead demands more variance.

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

Optimization · Pure Optimization
Tests daily-schedule routing and crafting-chain planning to engineer each escape.
Portal leans Optimization (Pure Optimization); The Escapists: The Walking Dead leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
The Escapists: The Walking Dead
Top-down movement with mild zombie-dodging pressure
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
No adversary modeling player.
The Escapists: The Walking Dead
Walkers are mindless scripted threats
The Escapists: The Walking Dead leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
The Escapists: The Walking Dead
Item spawns and walker placement vary modestly
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.
The Escapists: The Walking Dead
Crafting chains, schedules and escape routing are the whole game
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.