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

Optimization · Practiced Mastery
The genre-defining 3D open-world crime game set in Liberty City.

Execution · Practiced Mastery
Linear postwar crime story driven by cover shootouts and atmosphere.
Grand Theft Auto III leans Optimization (Practiced Mastery); Mafia II 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 III
Driving and clunky gunplay set a modest physical bar
Mafia II
Cover shooting and fistfight 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 III
Enemies are scripted; nothing models the player
Mafia II
Enemies are scripted
Grand Theft Auto III leans a little harder on variance, though the gap is small.
Grand Theft Auto III
Pedestrian and traffic chaos lightly randomises encounters
Mafia II
Story missions are fixed
Grand Theft Auto III leans a little harder on optimization, though the gap is small.
Grand Theft Auto III
Mission routing and city knowledge are learnable systems
Mafia II
Modest; learning encounter layouts
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.