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 GBA metroidvania built around collecting enemy souls.

Optimization · Pure Optimization
A free-form fantasy RPG where skill-leveling and spell-craft builds dominate.
Castlevania: Aria of Sorrow leans Optimization (Pure Optimization); The Elder Scrolls IV: Oblivion leans Optimization (Pure Optimization).
Castlevania: Aria of Sorrow leans a little harder on execution, though the gap is small.
Castlevania: Aria of Sorrow
Modest action timing
The Elder Scrolls IV: Oblivion
Real-time swing and block, modest demand
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania: Aria of Sorrow
Scripted enemies
The Elder Scrolls IV: Oblivion
Scripted enemies
Castlevania: Aria of Sorrow leans a little harder on variance, though the gap is small.
Castlevania: Aria of Sorrow
Soul drops are heavily random
The Elder Scrolls IV: Oblivion
Loot and level-scaling rolls
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania: Aria of Sorrow
Soul build crafting dominates
The Elder Scrolls IV: Oblivion
Skill leveling, spell crafting, exploit-prone builds
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.