head to head
Neither is simply harder - they are hard in different places. Portal 2 demands more execution; The Settlers: Rise of an Empire demands more reads.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.

Optimization · Pure Optimization
Optimising medieval production chains and settlement layouts at a gentle pace.
Portal 2 leans Optimization (Pure Optimization); The Settlers: Rise of an Empire leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Portal 2
Portal placement requires some precision but timing is lenient.
The Settlers: Rise of an Empire
Slow-paced building needs no dexterity
The Settlers: Rise of an Empire leans clearly harder on reads.
Portal 2
No opponent; puzzles are static.
The Settlers: Rise of an Empire
Multiplayer adds mild opponent anticipation, mostly economic
The Settlers: Rise of an Empire leans clearly harder on variance.
Portal 2
Puzzles are deterministic with no randomness.
The Settlers: Rise of an Empire
Map resources are scripted-but-unknown until scouted
Portal 2 leans a little harder on optimization, though the gap is small.
Portal 2
Solving the puzzle's logic IS the entire game.
The Settlers: Rise of an Empire
Settlement layout and production chains are the solvable core
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.