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.

Execution · Practiced Mastery
A near-future Call of Duty with squad-focused multiplayer and the Extinction mode.

Execution · Practiced Mastery
The sequel adding Horde mode to the campaign-plus-versus cover shooter formula.
Call of Duty: Ghosts leans Execution (Practiced Mastery); Gears of War 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.
Call of Duty: Ghosts
Fast time-to-kill rewards first-shot aim
Gears of War 2
Gnasher battles and movement tech set the ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Ghosts
Outguessing human routes and peeks matters
Gears of War 2
Human opponents in versus drive prediction play
Call of Duty: Ghosts leans a little harder on variance, though the gap is small.
Call of Duty: Ghosts
Spawns and lobby matchups add noise
Gears of War 2
Horde spawns add mild randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Ghosts
Loadout and map knowledge are solvable layers
Gears of War 2
Power-weapon timing and positioning are solvable
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.