head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, and it is a single point.

Execution · Pure Mechanics
Arcade run-and-gun whose one-credit clears demand total spawn memorization and twitch.

Execution · Practiced Mastery
A Cave bullet hell demanding the highest execution ceiling of any mainstream shmup, with a rank system that punishes passivity.
Metal Slug 3 leans Execution (Pure Mechanics); Mushihimesama leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug 3
one-hit deaths demand frame-level dodging and aim
Mushihimesama
Ultra Maniac difficulty requires inhuman movement precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug 3
every enemy wave is scripted
Mushihimesama
All bullet patterns are scripted Cave bullet-hell formations
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Slug 3
branching paths vary runs slightly
Mushihimesama
Rank system alters bullet speed based on play style
Mushihimesama leans a little harder on optimization, though the gap is small.
Metal Slug 3
memorizing spawns is the path to a one-credit clear
Mushihimesama
Shot type selection, rank management, and scoring routes are solvable
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.