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 · Practiced Mastery
A Cave bullet hell demanding the highest execution ceiling of any mainstream shmup, with a rank system that punishes passivity.

Execution · Pure Mechanics
A movement-shooter demanding near-perfect execution chains to maximise style rank against scripted but relentless enemies.
Mushihimesama leans Execution (Practiced Mastery); ULTRAKILL leans Execution (Pure Mechanics).
ULTRAKILL leans a little harder on execution, though the gap is small.
Mushihimesama
Ultra Maniac difficulty requires inhuman movement precision
ULTRAKILL
Style-ranked combat demands flawless movement, parries, and weapon-swap chains
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mushihimesama
All bullet patterns are scripted Cave bullet-hell formations
ULTRAKILL
All enemies are scripted; no adaptive human opponent exists
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mushihimesama
Rank system alters bullet speed based on play style
ULTRAKILL
Enemy placement is fixed and fully readable after one pass
Mushihimesama leans a little harder on optimization, though the gap is small.
Mushihimesama
Shot type selection, rank management, and scoring routes are solvable
ULTRAKILL
Weapon synergies and ranked-route planning form a deep solvable system
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.