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
Peak 16-bit run-and-gun of set-piece bosses and razor-thin dodges.

Execution · Pure Mechanics
Push-forward arena FPS where movement and aim are the whole game.
Contra III: The Alien Wars leans Execution (Pure Mechanics); DOOM (2016) leans Execution (Pure Mechanics).
Contra III: The Alien Wars leans a little harder on execution, though the gap is small.
Contra III: The Alien Wars
Relentless bosses and bullet dodging
DOOM (2016)
Aim, movement, glory-kill timing all peak.
DOOM (2016) leans a little harder on reads, though the gap is small.
Contra III: The Alien Wars
Set-piece bosses are pure scripts
DOOM (2016)
Demons scripted attack 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
DOOM (2016)
Minimal encounter randomness.
Contra III: The Alien Wars leans a little harder on optimization, though the gap is small.
Contra III: The Alien Wars
Weapon management and pattern memorization
DOOM (2016)
Rune and weapon mod picks meaningful.
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.