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

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

Execution · Pure Mechanics
Terry Cavanagh's minimalist reflex gauntlet of rotating walls measured in seconds survived.
DOOM (2016) leans Execution (Pure Mechanics); Super Hexagon leans Execution (Pure Mechanics).
Super Hexagon leans clearly harder on execution.
DOOM (2016)
Aim, movement, glory-kill timing all peak.
Super Hexagon
Sub-second reactions at extreme speed, pure reflex ceiling
DOOM (2016) leans a little harder on reads, though the gap is small.
DOOM (2016)
Demons scripted attack patterns.
Super Hexagon
No opponent, only walls
Super Hexagon leans a little harder on variance, though the gap is small.
DOOM (2016)
Minimal encounter randomness.
Super Hexagon
Pattern order randomized from a known set
DOOM (2016) leans clearly harder on optimization.
DOOM (2016)
Rune and weapon mod picks meaningful.
Super Hexagon
Pattern vocabulary is small, reaction is everything
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.