head to head
Grand Theft Auto V asks more than Just Cause 3, and the gap is reads.

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

Execution · Practiced Mastery
An explosion-first open-world sandbox starring an infinite-ammo wingsuit rebel.
Grand Theft Auto V leans Execution (Practiced Mastery); Just Cause 3 leans Execution (Practiced Mastery).
Grand Theft Auto V leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Just Cause 3
Wingsuit threading and tether stunts take practice
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Just Cause 3
Scripted military AI
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.
Just Cause 3
Emergent physics chaos, no real hidden info
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Heists, money loops, builds learnable.
Just Cause 3
Base liberation order and gear mod unlocks
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.