head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Optimization · Pure Optimization
Colour-painting terrain puzzles that resolve to finding the intended solution.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Nihilumbra leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
Nihilumbra leans a little harder on execution, though the gap is small.
Nihilumbra
Some platforming timing, but forgiving throughout
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Nihilumbra
Enemies cannot be fought or read, only avoided
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
The Elder Scrolls V: Skyrim leans a little harder on variance, though the gap is small.
Nihilumbra
Hand-designed puzzles with nothing random
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Nihilumbra
Choosing which colour solves each terrain puzzle is the game
The Elder Scrolls V: Skyrim
Skill stacking, enchant loops, and exploits are deeply solvable.
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.