head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Optimization · Pure Optimization
The genre-defining metroidvania with deep RPG systems.

Optimization · Practiced Mastery
The sequel adds minion mounts and an evil empire to corral with your goblin hordes.
Castlevania: Symphony of the Night leans Optimization (Pure Optimization); Overlord II leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania: Symphony of the Night
Forgiving action combat
Overlord II
Minion sweeps plus mounts need moderate control
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania: Symphony of the Night
Scripted bosses
Overlord II
Scripted empire enemies
Castlevania: Symphony of the Night leans a little harder on variance, though the gap is small.
Castlevania: Symphony of the Night
Item drops and rare gear
Overlord II
Deterministic encounters
Castlevania: Symphony of the Night leans a little harder on optimization, though the gap is small.
Castlevania: Symphony of the Night
Build crafting and sequence breaks
Overlord II
Minion management and domination choices are solvable
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.