head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Optimization · Pure Optimization
An open-world shooter-RPG won by perk routing and weapon mod optimization.

Optimization · Practiced Mastery
Expanded machine combat with broader build systems and traversal tools.
Fallout 4 leans Optimization (Pure Optimization); Horizon Forbidden West leans Optimization (Practiced Mastery).
Horizon Forbidden West leans a little harder on execution, though the gap is small.
Fallout 4
FPS aiming, VATS softens demand
Horizon Forbidden West
Faster combat with valor surges and aiming.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout 4
Scripted enemy AI
Horizon Forbidden West
Machines remain scripted, not adaptive.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout 4
Loot and legendary rolls
Horizon Forbidden West
Loot rolls and patrol RNG light.
Fallout 4 leans a little harder on optimization, though the gap is small.
Fallout 4
Perks, settlement, weapon mod planning
Horizon Forbidden West
Deeper gear, weapon techniques, machine weaknesses.
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.