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

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

Execution · Practiced Mastery
Piloting skill plus careful fuel and ammo routing across scripted missions.
Grand Theft Auto V leans Execution (Practiced Mastery); Nuclear Strike leans Execution (Practiced Mastery).
Nuclear Strike leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Nuclear Strike
Helicopter piloting and aimed strafing under fire demand steady hands
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Nuclear Strike
Enemy emplacements follow fixed scripts
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.
Nuclear Strike
Map layouts are unknown on first pass only
Nuclear Strike leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Nuclear Strike
Managing fuel, ammo and mission routing is the real layer
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.