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 genre-defining metroidvania with deep RPG systems.

Optimization · Pure Optimization
Villainous dungeon management game about luring monsters and crushing do-gooder heroes.
Castlevania: Symphony of the Night leans Optimization (Pure Optimization); Dungeon Keeper 2 leans Optimization (Pure Optimization).
Castlevania: Symphony of the Night leans a little harder on execution, though the gap is small.
Castlevania: Symphony of the Night
Forgiving action combat
Dungeon Keeper 2
Slap-and-drop micro and possession combat need quick hands.
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
Dungeon Keeper 2
Hero waves and rival keepers run on scripts.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania: Symphony of the Night
Item drops and rare gear
Dungeon Keeper 2
Hero party timing and creature moods vary mildly.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania: Symphony of the Night
Build crafting and sequence breaks
Dungeon Keeper 2
Dungeon layout, creature economy and research 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.