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

Execution · Practiced Mastery
Coordinating two-man cover tactics and aggro swaps through scripted firefights.

Execution · Practiced Mastery
Ballistic compensation and patrol memorisation along heavily scripted stealth corridors.
Army of Two: The 40th Day leans Execution (Practiced Mastery); Sniper: Ghost Warrior leans Execution (Practiced Mastery).
Sniper: Ghost Warrior leans a little harder on execution, though the gap is small.
Army of Two: The 40th Day
Cover shooting needs competent aim but generous systems forgive
Sniper: Ghost Warrior
Accounting for wind and drop on long shots demands steady aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Army of Two: The 40th Day
Enemy AI is scripted, co-op partner cooperates rather than opposes
Sniper: Ghost Warrior
Enemy AI runs scripted patrols, not adaptation
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Army of Two: The 40th Day
Encounters are scripted with minor spawn unknowns first time
Sniper: Ghost Warrior
Wind values add per-shot noise to compensate for
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Army of Two: The 40th Day
Aggro management and weapon upgrades reward planned coordination
Sniper: Ghost Warrior
Learning patrol routes and stealth paths solves each level
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.