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

Execution · Practiced Mastery
A co-op third-person shooter built around two mercenaries juggling enemy aggro together.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Army of Two leans Execution (Practiced Mastery); Grand Theft Auto V 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.
Army of Two
Cover shooting and co-op timing
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans a little harder on reads, though the gap is small.
Army of Two
Aggro system is mappable, not adaptive
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Army of Two
Scripted setpieces
Grand Theft Auto V
Some mission and lobby randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Army of Two
Weapon upgrades and aggro manipulation
Grand Theft Auto V
Heists, money loops, builds 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.