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 · Pure Mechanics
Flawless execution of memorised patterns under one-hit-death pressure.
Castlevania III: Dracula's Curse leans Execution (Pure Mechanics); Contra 4 leans Execution (Pure Mechanics).
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
Contra 4
One-hit deaths under dense bullet patterns demand near-perfect inputs
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
Contra 4
Every enemy and boss is a fixed 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
Contra 4
Spawns and patterns are identical every run
Castlevania III: Dracula's Curse leans a little harder on optimization, though the gap is small.
Castlevania III: Dracula's Curse
Partner choice, route branching, pattern memory
Contra 4
Memorising layouts and weapon routing enables the execution
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.