head to head
Neither is simply harder - they are hard in different places. DOOM (2016) demands more optimization; Millipede demands more variance.

Execution · Pure Mechanics
Push-forward arena FPS where movement and aim are the whole game.

Execution · Pure Mechanics
Raw arcade reflexes against accelerating swarms with mild spawn randomness.
DOOM (2016) leans Execution (Pure Mechanics); Millipede 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.
DOOM (2016)
Aim, movement, glory-kill timing all peak.
Millipede
Trackball precision under swarming pressure is everything
DOOM (2016) leans a little harder on reads, though the gap is small.
DOOM (2016)
Demons scripted attack patterns.
Millipede
Enemies follow fixed movement rules
Millipede leans clearly harder on variance.
DOOM (2016)
Minimal encounter randomness.
Millipede
Spawn waves and DDT timing vary run to run
DOOM (2016) leans clearly harder on optimization.
DOOM (2016)
Rune and weapon mod picks meaningful.
Millipede
Mushroom-field management is a thin strategic layer
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.