head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, and it is a single point.

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

Execution · Practiced Mastery
A cinematic open-world western leaning on shooting feel and atmosphere.
Grand Theft Auto IV leans Execution (Practiced Mastery); Red Dead Redemption 2 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 2
Gunplay and Dead Eye reward aim and timing.
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 2
Enemies use scripted AI patterns, not adaptation.
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 2
Some hunting and weather randomness, lightly hidden.
Red Dead Redemption 2 leans a little harder on optimization, though the gap is small.
Grand Theft Auto IV
Mission routing and weapon picks learnable.
Red Dead Redemption 2
Loadouts and routes solvable but loose.
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.