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

Optimization · Pure Optimization
Story-heavy deckbuilder of clashing dice and floor-by-floor library combat.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Library of Ruina leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans clearly harder on execution.
Library of Ruina
Turn-based card combat, no input precision.
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
Library of Ruina leans a little harder on reads, though the gap is small.
Library of Ruina
Scripted enemy decks, no adaptive opponent.
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
Library of Ruina leans clearly harder on variance.
Library of Ruina
Dice rolls and draws swing fights moderately.
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
Library of Ruina leans clearly harder on optimization.
Library of Ruina
Deck construction and clash math is deeply solvable.
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.