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
The classic AD&D CRPG where party planning beats dice luck over time.

Optimization · Systems & Chaos
An ARPG loot grind about chasing affix rolls to feed a damage-stack build.
Baldur's Gate leans Optimization (Pure Optimization); Diablo IV leans Optimization (Systems & Chaos).
Diablo IV leans a little harder on execution, though the gap is small.
Baldur's Gate
Pause-and-play needs minimal dexterity.
Diablo IV
Clicking and dodging are light; gear carries you.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Baldur's Gate
Scripted encounters, no adaptation.
Diablo IV
Enemies and bosses are scripted; no adaptive opponent.
Diablo IV leans a little harder on variance, though the gap is small.
Baldur's Gate
AD&D dice rolls throughout.
Diablo IV
Loot rolls, affixes, and uniques drive every session.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Baldur's Gate
Party builds and encounter prep solvable.
Diablo IV
Paragon, aspects, and damage buckets are solvable theorycraft.
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.