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
Side-on turn-based tactics where you manually aim ricocheting bullets for a steambot pirate crew.
Fallout 4 leans Optimization (Pure Optimization); SteamWorld Heist 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
SteamWorld Heist
Manual aim and ricochet shots reward steady hands
Fallout 4 leans a little harder on reads, though the gap is small.
Fallout 4
Scripted enemy AI
SteamWorld Heist
Enemy bots follow fixed behaviors
SteamWorld Heist leans a little harder on variance, though the gap is small.
Fallout 4
Loot and legendary rolls
SteamWorld Heist
Procedural ship layouts and loot drops
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
SteamWorld Heist
Crew builds, weapon picks, and turn routing carry runs
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.