head to head
Neither is simply harder - they are hard in different places. Infinifactory demands more optimization; The Elder Scrolls V: Skyrim demands more variance.

Optimization · Pure Optimization
A 3D factory-building puzzle where spatial reasoning and throughput efficiency are the entire challenge.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Infinifactory leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans a little harder on execution, though the gap is small.
Infinifactory
Block placement has no timing pressure
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.
Infinifactory
No opponent; alien factory puzzle game
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
The Elder Scrolls V: Skyrim leans clearly harder on variance.
Infinifactory
Build targets are fixed and deterministic
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
Infinifactory leans clearly harder on optimization.
Infinifactory
Engineering 3D factory lines that assemble alien products correctly and efficiently
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.