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 · Practiced Mastery
Crafting absurd weapons and routing a zombie-filled city against the clock.

Optimization · Pure Optimization
An open-world shooter-RPG won by perk routing and weapon mod optimization.
Dead Rising 3 leans Optimization (Practiced Mastery); Fallout 4 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.
Dead Rising 3
Crowd fighting takes modest aim and dodge timing
Fallout 4
FPS aiming, VATS softens demand
Fallout 4 leans a little harder on reads, though the gap is small.
Dead Rising 3
Zombies and psychopaths run fixed scripts, never adapt
Fallout 4
Scripted enemy AI
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dead Rising 3
Weapon and blueprint locations are unknown until explored
Fallout 4
Loot and legendary rolls
Fallout 4 leans a little harder on optimization, though the gap is small.
Dead Rising 3
Combo weapon crafting and timed routing drive efficient runs
Fallout 4
Perks, settlement, weapon mod planning
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.