head to head
Neither is simply harder - they are hard in different places. Portal demands more optimization; The Dwarves demands more variance.

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

Optimization · Pure Optimization
Tactical crowd-battle planning - hero composition and ability timing against scripted hordes.
Portal leans Optimization (Pure Optimization); The Dwarves leans Optimization (Pure Optimization).
Portal leans a little harder on execution, though the gap is small.
Portal
Portal placement timing modest.
The Dwarves
Real-time crowd battles reward timely ability triggers
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 Dwarves
Orc hordes follow scripted attack logic
The Dwarves leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
The Dwarves
Encounter compositions are known after one attempt
Portal leans clearly harder on optimization.
Portal
Pure puzzle-solving optimization.
The Dwarves
Hero picks, skill timing and crowd physics positioning decide fights
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.