head to head
Neither is simply harder - they are hard in different places. Farthest Frontier demands more variance; Portal 2 demands more execution.

Optimization · Pure Optimization
Building a frontier settlement where food diversity, disease prevention, and defensive layout must be solved simultaneously.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Farthest Frontier leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Farthest Frontier
All construction and assignment decisions are deliberate and pauseable
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.
Farthest Frontier
Raider and animal threats follow scripted spawn rules
Portal 2
No opponent; puzzles are static.
Farthest Frontier leans clearly harder on variance.
Farthest Frontier
Disease outbreaks, wild animal raids, and harvest yields add uncertainty
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans a little harder on optimization, though the gap is small.
Farthest Frontier
Crop rotation, food variety, and building placement are deeply 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.