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

Optimization · Pure Optimization
A notoriously difficult comedy adventure where Rincewind the inept wizard must rid Ankh-Morpork of a dragon.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Discworld leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans clearly harder on execution.
Discworld
Point-and-click; no manual ceiling.
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.
Discworld
Ankh-Morpork's citizens are scripted gag dispensers.
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
Discworld leans clearly harder on variance.
Discworld
Infamously obscure puzzle logic blindsides every first-timer.
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.
Discworld
Byzantine item chains are brutal but fully 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.