head to head
Neither is simply harder - they are hard in different places. Portal 2 demands more optimization; The Dwarves demands more variance.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.

Optimization · Pure Optimization
Tactical crowd-battle planning - hero composition and ability timing against scripted hordes.
Portal 2 leans Optimization (Pure Optimization); The Dwarves leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Portal 2
Portal placement requires some precision but timing is lenient.
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 2
No opponent; puzzles are static.
The Dwarves
Orc hordes follow scripted attack logic
The Dwarves leans clearly harder on variance.
Portal 2
Puzzles are deterministic with no randomness.
The Dwarves
Encounter compositions are known after one attempt
Portal 2 leans clearly harder on optimization.
Portal 2
Solving the puzzle's logic IS the entire game.
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.