head to head
Neither is simply harder - they are hard in different places. Arcanum: Of Steamworks and Magick Obscura demands more variance; Portal demands more execution.

Optimization · Pure Optimization
A Victorian-era RPG where the magic-versus-tech split and schematic mastery reward deep system optimization.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Arcanum: Of Steamworks and Magick Obscura leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Arcanum: Of Steamworks and Magick Obscura
Real-time mode is optional; turn-based eliminates all twitch
Portal
Portal placement timing modest.
Arcanum: Of Steamworks and Magick Obscura leans a little harder on reads, though the gap is small.
Arcanum: Of Steamworks and Magick Obscura
All NPCs and factions follow scripted dialogue and combat routines
Portal
No adversary modeling player.
Arcanum: Of Steamworks and Magick Obscura leans clearly harder on variance.
Arcanum: Of Steamworks and Magick Obscura
Hidden technology diagrams and faction reaction thresholds create exploration unknowns
Portal
Deterministic chambers; no randomness.
Arcanum: Of Steamworks and Magick Obscura leans a little harder on optimization, though the gap is small.
Arcanum: Of Steamworks and Magick Obscura
Magic versus technology stat split and schematic discovery are deeply optimizable
Portal
Pure puzzle-solving optimization.
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.