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

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

Optimization · Pure Optimization
A turn-based tactics RPG about exploiting terrain and squad synergies.
Portal leans Optimization (Pure Optimization); Urtuk: The Desolation leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Urtuk: The Desolation
Turn-based, so no reflex or aim skill
Urtuk: The Desolation leans a little harder on reads, though the gap is small.
Portal
No adversary modeling player.
Urtuk: The Desolation
Enemy AI is scripted, not adaptive to you
Urtuk: The Desolation leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Urtuk: The Desolation
Battlefield generation and crit rolls add randomness
Urtuk: The Desolation leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Urtuk: The Desolation
Exploiting terrain, traits and positioning is the entire 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.