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

Optimization · Practiced Mastery
A stylish side-scrolling stealth game where a rogue agent sabotages both Cold War superpowers.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
CounterSpy leans Optimization (Practiced Mastery); Grand Theft Auto V 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.
CounterSpy
Cover shooting and quick takedowns need decent reflexes
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
CounterSpy
Guard AI is simple and predictable
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
CounterSpy leans clearly harder on variance.
CounterSpy
Procedurally assembled levels stay unknown until entered
Grand Theft Auto V
Some mission and lobby randomness.
CounterSpy leans clearly harder on optimization.
CounterSpy
Managing DEFCON risk and weapon plans is systematic
Grand Theft Auto V
Heists, money loops, builds learnable.
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.