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

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

Execution · Practiced Mastery
Bullet-hell metroidvania whose bunny-girl bosses fill the screen with patterns.
Grand Theft Auto V leans Execution (Practiced Mastery); Rabi-Ribi leans Execution (Practiced Mastery).
Rabi-Ribi leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Rabi-Ribi
Dense bullet-hell boss patterns demand precise dodging.
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Rabi-Ribi
Boss patterns are fixed and memorizable.
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.
Rabi-Ribi
Exploration unknowns on first run.
Rabi-Ribi leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Rabi-Ribi
Sequence-breaking routes and boss pattern study converge to mastery.
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.