head to head
Neither is simply harder - they are hard in different places. Discworld demands more variance; Portal 2 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
A first-person puzzle game where seeing the solution is the whole skill.
Discworld leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Discworld
Point-and-click; no manual ceiling.
Portal 2
Portal placement requires some precision but timing is lenient.
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.
Portal 2
No opponent; puzzles are static.
Discworld leans clearly harder on variance.
Discworld
Infamously obscure puzzle logic blindsides every first-timer.
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Discworld
Byzantine item chains are brutal but fully solvable.
Portal 2
Solving the puzzle's logic IS the entire game.
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.