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

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

Execution · Practiced Mastery
A neo-noir one-hit-kill action platformer about planning and replaying perfect assassinations.
Grand Theft Auto V leans Execution (Practiced Mastery); Katana ZERO leans Execution (Practiced Mastery).
Katana ZERO leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Katana ZERO
One-hit-death slashing and deflects demand precision
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Katana ZERO
Enemies follow fixed placements and behaviours
Grand Theft Auto V leans a little harder on variance, though the gap is small.
Grand Theft Auto V
Some mission and lobby randomness.
Katana ZERO
Rooms are identical on every attempt
Katana ZERO leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Katana ZERO
Planning the perfect room-clear sequence
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.