head to head
Metal Gear Solid 4: Guns of the Patriots asks more than Army of Two, and the gap is optimization.

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

Optimization · Practiced Mastery
Series finale blending stealth with active battlefields and heavy cinematics.
Army of Two leans Execution (Practiced Mastery); Metal Gear Solid 4: Guns of the Patriots leans Optimization (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
Metal Gear Solid 4: Guns of the Patriots
flexible gunplay alongside sneaking
Army of Two leans a little harder on reads, though the gap is small.
Army of Two
Aggro system is mappable, not adaptive
Metal Gear Solid 4: Guns of the Patriots
battlefield factions act on scripts
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
Metal Gear Solid 4: Guns of the Patriots
mid-battle chaos mostly cosmetic
Metal Gear Solid 4: Guns of the Patriots leans clearly harder on optimization.
Army of Two
Weapon upgrades and aggro manipulation
Metal Gear Solid 4: Guns of the Patriots
camo, gear, and route knowledge per act
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.