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

Execution · Pure Mechanics
The hardest NES Castlevania, with branching routes and switchable partner characters.

Execution · Practiced Mastery
Modern stylish-action peak with three playstyles and a combo ceiling players are still climbing.
Castlevania III: Dracula's Curse leans Execution (Pure Mechanics); Devil May Cry 5 leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania III: Dracula's Curse
Brutal platforming and tight whip timing throughout
Devil May Cry 5
Three movesets and Royal Guard frames set a towering ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania III: Dracula's Curse
Scripted enemies and bosses only
Devil May Cry 5
Even Vergil's mirror fight is a learnable script
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania III: Dracula's Curse
Minor enemy spawn wobble
Devil May Cry 5
V's summons add flavor, not randomness that matters
Devil May Cry 5 leans a little harder on optimization, though the gap is small.
Castlevania III: Dracula's Curse
Partner choice, route branching, pattern memory
Devil May Cry 5
Loadouts, breakers, and enemy-specific tech reward deep study
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.