head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Mushihimesama demands more execution.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Execution · Practiced Mastery
A Cave bullet hell demanding the highest execution ceiling of any mainstream shmup, with a rank system that punishes passivity.
Grand Theft Auto V leans Execution (Practiced Mastery); Mushihimesama leans Execution (Practiced Mastery).
Mushihimesama leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Mushihimesama
Ultra Maniac difficulty requires inhuman movement precision
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
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.
Grand Theft Auto V
Some mission and lobby randomness.
Mushihimesama
Rank system alters bullet speed based on play style
Mushihimesama leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
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.