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.

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

Execution · Practiced Mastery
High-speed cyborg slasher built on precise parries and slicing anything in half.
Castlevania III: Dracula's Curse leans Execution (Pure Mechanics); Metal Gear Rising: Revengeance leans Execution (Practiced Mastery).
Castlevania III: Dracula's Curse leans a little harder on execution, though the gap is small.
Castlevania III: Dracula's Curse
Brutal platforming and tight whip timing throughout
Metal Gear Rising: Revengeance
parry timing and blade-mode cuts demand sharp reactions
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
Metal Gear Rising: Revengeance
bosses telegraph fixed patterns
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
Metal Gear Rising: Revengeance
deterministic encounters
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Castlevania III: Dracula's Curse
Partner choice, route branching, pattern memory
Metal Gear Rising: Revengeance
learning movesets and upgrade priorities
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.