head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Yet Another Zombie Defense demands more optimization.

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

Execution · Practiced Mastery
A twin-stick survival game testing base-layout economy and sustained horde aim.
Grand Theft Auto V leans Execution (Practiced Mastery); Yet Another Zombie Defense leans Execution (Practiced Mastery).
Yet Another Zombie Defense leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Yet Another Zombie Defense
Twin-stick aim under swelling night hordes carries survival
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Yet Another Zombie Defense
Zombies beeline mindlessly, never adapting
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.
Yet Another Zombie Defense
Wave composition varies modestly between runs
Yet Another Zombie Defense leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Yet Another Zombie Defense
Turret placement and barricade economy decide how long you last
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.