head to head
Red Dead Redemption asks more than Grand Theft Auto IV, and the gap is optimization.

Execution · Practiced Mastery
A grittier crime story where weighty driving and gunplay carry the experience.

Execution · Practiced Mastery
Open-world western about an outlaw forced to hunt down his old gang.
Grand Theft Auto IV leans Execution (Practiced Mastery); Red Dead Redemption 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.
Grand Theft Auto IV
Heavier driving and cover shooting reward control.
Red Dead Redemption
Dead Eye softens but gunplay still wants aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto IV
Scripted AI, no adaptive opponent modeling.
Red Dead Redemption
Multiplayer skirmishes add light human prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto IV
Minor mission variance.
Red Dead Redemption
Ambient events and spawns vary mildly
Red Dead Redemption leans clearly harder on optimization.
Grand Theft Auto IV
Mission routing and weapon picks learnable.
Red Dead Redemption
Mission approaches and economy are 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.