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
The deepest optimization puzzle in the Infinity Engine lineage, rewarding encyclopedic knowledge of 2nd Edition AD&D systems.

Optimization · Pure Optimization
The genre-defining loot ARPG whose builds, runes, and trade economy players still optimize decades later.
Baldur's Gate II: Shadows of Amn leans Optimization (Pure Optimization); Diablo II 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.
Baldur's Gate II: Shadows of Amn
Pause-and-plan removes twitch entirely; micro-placement has marginal value
Diablo II
Positioning and potion reflexes, little else physical
Baldur's Gate II: Shadows of Amn leans a little harder on reads, though the gap is small.
Baldur's Gate II: Shadows of Amn
Enemies run scripted behaviour patterns, never modelling your tactics
Diablo II
Monster AI is fully mappable
Diablo II leans a little harder on variance, though the gap is small.
Baldur's Gate II: Shadows of Amn
Loot randomization and enemy ability use create hidden-information layers
Diablo II
Loot RNG and random maps drive the grind
Baldur's Gate II: Shadows of Amn leans a little harder on optimization, though the gap is small.
Baldur's Gate II: Shadows of Amn
Mage spell sequences, dual-class builds and Spellhold routing define mastery
Diablo II
Builds, breakpoints, rune economy, magic-find routing are the game
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.