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

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

Optimization · Pure Optimization
A musou spinoff of Fire Emblem: Three Houses blending hack-and-slash combat with light tactics.
Fallout 4 leans Optimization (Pure Optimization); Fire Emblem Warriors: Three Hopes leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout 4
FPS aiming, VATS softens demand
Fire Emblem Warriors: Three Hopes
Real-time combat is forgiving hack-and-slash
Fallout 4 leans a little harder on reads, though the gap is small.
Fallout 4
Scripted enemy AI
Fire Emblem Warriors: Three Hopes
Enemy commanders follow scripted AI
Fallout 4 leans a little harder on variance, though the gap is small.
Fallout 4
Loot and legendary rolls
Fire Emblem Warriors: Three Hopes
Minor drop and recruitment randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Fallout 4
Perks, settlement, weapon mod planning
Fire Emblem Warriors: Three Hopes
Class builds, unit orders, weapon triangle, map management decide battles
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.