head to head
iRacing asks more than Grand Theft Auto V, and the gap is execution.

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

Execution · Practiced Mastery
Hardcore online racing sim with PvP wheel duels.
Grand Theft Auto V leans Execution (Practiced Mastery); iRacing leans Execution (Practiced Mastery).
iRacing leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
iRacing
Brutally precise wheel inputs required
iRacing leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
iRacing
Serious wheel-to-wheel racing vs humans
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.
iRacing
Weather, tire wear, mechanical variance
iRacing leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
iRacing
Setup, strategy, iRating progression
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.