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

Execution · Pure Mechanics
VR rhythm game about slicing color-coded blocks to music with lightsabers.

Execution · Pure Mechanics
Push-forward arena FPS where movement and aim are the whole game.
Beat Saber leans Execution (Pure Mechanics); DOOM (2016) leans Execution (Pure Mechanics).
Beat Saber leans clearly harder on execution.
Beat Saber
Pure full-body rhythm precision at speed
DOOM (2016)
Aim, movement, glory-kill timing all peak.
DOOM (2016) leans a little harder on reads, though the gap is small.
Beat Saber
No opponent of any kind
DOOM (2016)
Demons scripted attack patterns.
DOOM (2016) leans a little harder on variance, though the gap is small.
Beat Saber
Patterns are fully known and fixed
DOOM (2016)
Minimal encounter randomness.
DOOM (2016) leans clearly harder on optimization.
Beat Saber
Swing-angle scoring technique and map 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.