head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Pure Mechanics
Peak 16-bit run-and-gun of set-piece bosses and razor-thin dodges.

Execution · Pure Mechanics
Brutal one-hit-death shmup execution over patterns that must be memorised to survive.
Contra III: The Alien Wars leans Execution (Pure Mechanics); Silver Surfer 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.
Contra III: The Alien Wars
Relentless bosses and bullet dodging
Silver Surfer
One-hit deaths demand near-perfect dodging every second
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Contra III: The Alien Wars
Set-piece bosses are pure scripts
Silver Surfer
Enemy waves are fully scripted patterns
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Contra III: The Alien Wars
Everything is fixed and learnable
Silver Surfer
Stages replay identically once learned
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Contra III: The Alien Wars
Weapon management and pattern memorization
Silver Surfer
Memorising spawn patterns and safe lines is mandatory 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.