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
A pure loot-and-build treadmill where set-bonus optimisation and Rift pushing define performance.

Optimization · Pure Optimization
Using stealth-phase positioning to construct optimal ambushes against scripted patrols.
Diablo III leans Optimization (Pure Optimization); Mutant Year Zero: Road to Eden leans Optimization (Pure Optimization).
Diablo III leans a little harder on execution, though the gap is small.
Diablo III
Greater Rift pushing has minor mechanical demand in builds
Mutant Year Zero: Road to Eden
Stealth positioning before combat demands spatial precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
No meaningful adaptive opponent; co-op is cooperative
Mutant Year Zero: Road to Eden
Enemies patrol fixed routes; no adaptive opponent modeling
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
Primal Ancient drops and set dungeon RNG drive the grind
Mutant Year Zero: Road to Eden
Hit chances and mutation procs introduce meaningful RNG
Diablo III leans a little harder on optimization, though the gap is small.
Diablo III
Set bonuses and paragon levelling are almost entirely solvable
Mutant Year Zero: Road to Eden
Stalker trait loadouts and pre-combat positioning are tight optimization puzzles
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.